I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.
- William Blake
Friday, November 23, 2018
1: Maximum damage.
2: Double damage.
3: Triple damage;
4: Special (depends on weapon, armor, etc).
Example: if your usual damage is 1d6+3, maximum damage is 9, double damage is 2d6+6* (Average 13), triple damage is 3d6+9* (average 19.5).
*OR just roll 1d6+3 and multiply by two or three.
A super-critical is achieved when you crit and beat the target AC by 10 or more, or when you have advantage an roll 20 on both dice. In some circumstances, all your crits will be super-crits, while in others none will (however, you can reach crits through combos - see my next post).
I thought of this as a rule for my Dark Fantasy Basic but you can obviously use for D&D 5e, etc. Notice that "maximum damage" result is slightly worse than the usual 5e crit... but it kinda FEELS better IMO, and is one less roll.
I just like crits! They are exciting, fun and a great way of differentiating weapons and characters, since only a few hits will be crits. It also gives you that "urgency" - the fight may suddenly take a sharp turn for the better or worse...
However, I get bored by long tables and dislike stopping combats to check complex rules/charts.
Super-crits are intuitive and significant. "Special" results - you can put whatever you want there, but should be very significant, and maybe IN ADDITION to triple damage - will happen less than 2% of the time. THEN you can use a table or complex rules. Almost 99% of the time, things will be straightforward.
Notice that this crits will make the difference between creatures of different HD/CR more significant. A level 10 fighter will be very likely to destroy one orc per critical hit in 5e - or even an ogre (4+1 HD) in B/X or DFB.
Likewise, heroes must think twice before attacking something that is out of their league. In 5e, this means the need for "minions" for high-CR foes is made a bit less relevant.
Well, that's it for now.
Monday, November 12, 2018
Here is a small part from TERATOGENICON, the ultimate monster generator! If you like it, consider acquiring the book on DTRPG. I wrote this post before publishing the book, so some of the text has been update. The tables and pages you see below are exactly as presented in the book.
(The images are copyright WotC, as far as I can tell, and are not included in the book - which is lavishly illustrated by Rick Troula!)
Saturday, November 03, 2018
Habits, diet and habitat
Appearance & Powers
Origins and goals
Saturday, October 20, 2018
Aberrations are the strangest and most variable type of monster. A giant with two heads or blue skin is still a giant; a giant with a head on its stomach, a serpent for a tongue and half a dozen slimy tentacles where the legs should be is probably an aberration.
Habits, diet and habitat
Friday, October 12, 2018
Every fight begins with a fast turn. After this turn, everybody takes a slow turn, and so on.
In a fast turn, you can move half your speed (round down), make half you attacks (round down), etc.
In a slow turn, you can do the same, but round up. Most actions happen in the slow turn, but, like attacks, they are subjected to "halving" if possible (if you choose to "Dash", for example, you just double your movement for both turns).
It is very likely that you have to declare your action during or after the fast turn.
Let us say a fighter has three attacks and moves 35 feet in a turn: he could move 15 feet and attack once in a fast turn, and move 20 feet and attack twice in a slow turn.
As I've said,the problem is not easy to solve - but easy enough to reduce by half.
For example, instead of of having a whole turn where you get up, move 15 feet, and attack you opponent three times while he DOES NOTHING, a more "organic" solution would be something like: you move 10 feet, he moves 5 feet, you attack twice, he attacks once, you attack once more, then he attacks, etc.
The inspiration for this idea is Shadow of the Demon Lord, BTW.
Two guys are facing each other, 30 feet apart. One has a dagger, the other a halberd. Who hits first? Obviously, the halberd (unless you THROW the dagger, which is an interesting distinction); but most RPGs that get to this level of detail say that the dagger attacks first (this includes the 5e DMG optional rules).
Which is why I'd say weapon speed shouldn't be about who attacks FIRST, but who attacks AGAIN first. The guy with the halberd might hit first, but the guy with a dagger could stab a foe three times during one halberd swing.
Easiest way to do this: a critical hit gives you a CHANCE to attack again. The faster the weapon (an the greater the number of attack you have), the greater the chance. Or, to make things faster, the GM could roll a single dice every round: every weapon with a speed above that threshold gains an extra attack.
If you want to account for weapon reach, being approached by a foe with a shorter weapon allows you to attack first if you're not engaged with anyone else (an opportunity attack would be an appropriate alternative to this).
Spells and spell interruption
I like the idea of spell interruption, which is not an important thing in D&D 5e. In this system, you could probably choose a spell to use in your fast turn, and only "fire" it in a slow turn. Alternatively, you could only use spells of a (spell slot) level that is half your maximum in your fast turns. For example, if you can cast 9th level spells, you could cast a 4th level spell in your fast turn, OR prepare a 9th level spell to cast in your slow turn.
I'm tempted to say that, in the first case, you could ALSO cast ANOTHER 4th level spell in your slow turn - provided you didn't lose concentration between turns.
Bonus actions/reactions/object interactions
I would probably allow reaction in BOTH rounds. Seems to me that it would be a welcome addition. Same goes for object interactions.
Bonus actions are trickier; limiting to one per round seems more reasonable, but see below.
One way to make this system more tactical is allowing some choice. Usually, you can move AND attack, but if you decide not to move, maybe you can take an additional bonus action (not more than one bonus action per turn), cast an additional spell (4th+4th, as seem below), or make an attack in your fast turn, if you have a single attack. If you have multiple attacks, you could use a crossbow multiple times without moving, or a net and trident, etc.
- Shorter turns means players pay more attention.
- The "ready" action makes a bit more sense.
- Tactical choices.
- Organic movement./attacks.
- Spell interruption.
- Interesting use for low-level spells at high levels.
- Action Surge looks better.
- TWF could be "fixed" by something like this (more object interactions, more bonus actions, etc). Same goes for crossbow, net, etc.
- More straightforward than checking the DMG table.
Frankly, this level of detail isn't appreciated by many, and I'm not sure I'm willing to put up with it. "old school" initiative, with phases and all, still sound a bit simpler to me. Still, for a combat-oriented game, I feel this could be fun.
Saturday, October 06, 2018
Saturday, September 29, 2018
Silliness aside, it is a (somewhat) interesting topic that resurfaces from time to time. "D&D is not a role-playing game", some say, "because you are not role-playing when you're rolling dice". Or something to that effect. Maybe I can't make the best "iron man" version of this argument, but I'll try - and you're welcome to improve the argument in the comments.
It goes more or less like this:
There are two things you do when you play RPGs:
A) playing the mechanics* (using your character sheet, dice etc.);
B) "actual" role-playing - in-character conversation, making decisions as your PC, etc. (without using you dice, token, character sheets, etc);
* Mechanics aren't limited to dice - automatic successes, fate points, jenga towers and even "the DM decides how many HPs the monster has" are mechanics.
The argument of ten focuses on the distinctions between the two, as if they were two separate things. Something like "D&D is not an RPG because if focuses on A, not B". Maybe "true" RPGs is something like improvisational theater which requires no written rules or even arbiters.
|D&D without any mechanics - "I kill the dragon with one blow".|
For example, you could have a situation such as this:
> The goblin says "get out of my way".
> Player says: "I flex my muscles and tell him that in Cimmeria we eat goblins for breakfast".
No dice rolled, no looking at the sheet - BUT the player is ROLE-PLAYING a strong barbarian warrior, in a way he COULDN'T do if his sheet says "Str 8 wizard". So, the mechanics are IMPLIED even if not being used at the time.
If you have ONLY mechanics, it would make sense to say you aren't playing a RPG. A good example would be HeroQuest (the board game, not the RPG): it has a lot more in common with chess than with D&D.
|Great game, BTW|
In RPGs you must make most of your decisions AS A CHARACTER. Here is one common example of this confusion, which I mentioned recently:
GM: You enter the room... there is a strange altar on the middle of it.
Player: Can I roll Arcana?
GM: No. Describe what you're trying to do instead.
In this example, the player is obviously taking a choice from the player POV, not the character's. What we do is something like:
GM: You enter the room... there is a strange altar on the middle of it.
Player: Do I know if this altar was used for magic?
GM: Probably, there are mystic runes carved in it... (and then maybe roll arcana to identify them, etc.).
But this is not black and white. RPGs will always be a bit of an "hybrid" between "A" and "B". Sometimes, you might use the mechanics without regards for the role-playing ("I use inspiration to make a re-roll"), and sometimes you will "role-play" without any reference to the mechanics ("I ask the friendly vendor how much the cabbage costs"*).
* Notice that if you wanna haggle or lie to the vendor, mechanics might come into play. And this isn't a new-school thing - in OD&D, your charisma score (a mechanic) could determine if a witch would keep you as a lover or killed you.
And this, my friends, in why D&D is, indeed, a role-playing game.
Friday, September 21, 2018
Anyway, he posted the whole thing (only 6 pages or so) on youtube. A review would be a bit useless: the book is awesome and incredibly clever; go check it out.
But it got me thinking on how I would do a minimalist, equipment-based version of D&D.
3d6 in order. Modifiers are new-school style (+1 for 12/13, +2 for 14/15, etc.), but, to make things simpler, no negative modifiers.
Since abilities are so central, everything would be roll-under (roll 1d20 under you ability score to succeed), like Moldvay suggests. This would include saves, attacks and spells.
An ability of 3 would be very hindering regardless of the +0 modifier.
Natural 1 is a critical hit. Probably double damage. No need for "fumbles".
Here is how I'd use abilities to keep things nice and symmetric:
Encumbrance and armor
Encumbrance is central in such an equipment-focused game, and I obviously like the idea of encumbrance slots.
I'd be tempted to go one step further in the direction of videogames and give body, legs, chest, arms and head "slots" for armor, each with a +1 AC bonus. So a naked warrior with helmet and shield would get +2. A well-armored fighter would have greaves, bracers, body armor (chain?), breastplate and helmet, for a total of +5 or maybe +6. Shield would also count as secondary weapon.
However... just listing different types of armors with different weights, each giving a +1 point of AC per "slots" would be simpler.
Dexterity would give you an armor bonus... provided you have enough EMPTY slots as suggested in the link above.
Attacks are opposed rolls: if the attacker hits, the defender gets to roll "dodge", which will only be successful if lower than AC but higher than the attacker's roll.
Or just get rid of armor AC and do damage reduction instead. Seems fitting.
Weapons and abilities
Since the game is about abilities and inventory, I would make them interact a bit more: maybe limit weapon damage to you Strength score, so carrying a 1d8 blade would be less useful if you have Strength 5, add "finesse" weapons that use Dexterity instead of Strength, and so on.
Roll under Intelligence to cast a spell. Any spell.
One interesting thing about knave is that, to use spells, you need to carry spell-books. So "spell slots" are actually... encumbrance slots! Nice! However, you can only use each book once a day. Your grimoires get "bricked" after one use. Not ideal, IMO. How about magic points, to mirror hit points? Each use costs one magic point per spell level. Fail and lose twice that much. Less than 0 means terrifying death, or worse. Or maybe let the spell turn against the caster in that case - better have high Charisma then!
Magic points need SOME use for non-magicians. So maybe they are some kind of "luck points" or "willpower", and can be used for re-rolls, etc.
Charisma protects you from magic. Seems fitting with roguish heroes. "Physical" magic might allow you to roll DEX instead.
Tools instead of skills
Since there are no skills, 5e's concept of tools would fit perfectly here. A medicine kit instead of a healing skill, and so on.
Since we got rid of classes, why not go further and get rid of levels? Every significant "goal" achieved (a couple of short adventures, etc.) allows everyone in the group to augment one ability by one (maximum 20, although rolling a 20 is automatic failure anyway), and the person with the least ability score sum to augment two abilities.
For epic monsters, additional Strength (say, Strength 28 for an ancient dragon) could cause it to crit on an 8 or less.
No hit points?
Numbers would be lower across the board. A dragon causing, say, 1d6+9 damage would be scary for everyone. And with 24 (+6) Constitution, would ignore all attacks that cause six point of damage or less.
Spells would have to be nerfed as well; maybe 1d6+spell level damage would be enough, provided you can hit lots of targets with a fireball. A magic wand or staff could allow you to cast 0-level "missiles" doing 1d6 damage.
What's the point?
Sunday, September 16, 2018
He touches on lots of interesting points there: rulings versus rules, "narrative", options (and maybe the paradox of choice) and mechanics versus "identity".
I am a bit curious about this bit:
On one ahnd, I agree that the GM is the only one to turn to for mechanical answers. However, in a game as complex as 5e, IF I were to follow the rules strictly (which I don't), I would ask THE PLAYERS to know their own rules (as pertaining to their PCs) since I'm incapable of keeping track of the (literally) dozens of features and powers that a party of four 5th level characters have.
There is also "who you are is more important than what you do". Sounds like something anathema to old school play, where what you DO during the game is more important than what you character is, since your character isn't special.
However, in this context, it seems that Mearls is advocating for something like one mechanic per (archetypal) trait, something I obviously agree with. I'm doubtful if 5e achieved that - it has enough mechanics that seem to indicate nothing within the fictional word - but it is certainly an improvement over 3e and 4e in this aspect.
There is also this last part:
I like the fact that Mearls wants to do away with the insanity of 3e purposefully (?) adding bad feats to the game*, but TBH I wished that "mechanical expertise" was kept to a minimum instead of simply being "balanced" (which doesn't mean much).
[*to be fair, there are lots of people saying that this isn't what Cook meant. I still think toughness is a stupid feat that shouldn't exist, but Justin Alexander makes a good point]
Playing D&D - or being good at playing D&D - should be about being creative, fun, and using the fictional world in awesome ways, not knowing your ways around the rules (we have a GM for that) or looking for loopholes and combos to make your character more powerful. Loopholes in the fiction can be awesome ("So he cannot be killed by a mortal man? Good thing I'm a woman!"), loopholes in the mechanics are a lot less so.
The "mechanical expertise" part is also a bit discouraging to newbies, specially if they feel that they must be experts on 400 pages of mechanics to enjoy D&D. This is not the case at all.
All in all, I'm happy that Mearls and Crawford have taken 5e to a more straightforward and, in many ways, old school approach.
As always, I'm not sure that it actually beats Basic D&D, since many WotC-ism that I dislike were kept in the game. For me, its back to "playing 5e the old school way" or just going with Dark Fantasy Basic, my 5e+B/X mashup.
But hey - that's just us! Individual groups have different experiences and all...
Friday, August 31, 2018
I was starting a new campaign and had to choose between 5e and Dark Fantasy Basic (DFB), my BX clone.
I had one new player in my group, to whom I had never GMed to, and everybody was more familiar with "official" D&D. Another player wanted to make a gnoll PC, which unfortunately isn't a thing that exists in DFB (yet). So I thought 5e would be a better fit for everybody.
We spent most of the session choosing features and spells for the new characters (the warlock was a hassle). Having options is nice, but going though a dozen classes and more than a dozen races (had Volo's on the table... sigh) didn't improve the enjoyment of the game.
Luckily we rolled stats randomly (with 5e quick characters) skipped feats, flaws, etc. In the end, we manage to play a bit less than two hours (we had four to begin with).
During the game, I went full "YES, you can" and "NO, we don't need to check the rules" on the players.
Player: Which weapons can my warlock use?
GM: You have 10 Dex and 10 Str... Just pick any weapon you want.
Player: Can my 1st level spell identify if this plant is poisonous?"
GM: I don't remember... but you're a druid spending a spell slot, of course it can.
Player: Can my barbarian pick the snake-demon and thrown it across the room in one turn? How does grappling work in 5e again?
GM: Just make an athletics check and we'll see.
I do not pull punches against the PCs when running adventures, but it seems I cannot be bothered to check the books during play anymore, and I err on the side of "of course you can". Like I've said in the latest post, the NPCs play by the same rules (or lack of thereof)!
I also (half-jokingly) went through the whole "the dice do nothing" exchange during the game:
Player: Can I roll Arcana?
GM: Good for you. Now, describe what you're trying to do instead.
BTW, the fact that the character was a gnoll didn't come up even once in the session. Nor did any of the other races (aasimar and tiefling... yeah). Except for the goliath, who had disadvantage fighting witg a greataxe in a narrow corridor... which was fun, but I'm pretty sure is not in the actual rules of the game.
In short, WotC D&D has many different options, but that doesn't necessarily means more enjoyment - even though I REALLY LIKE having options.
And RAW has almost no place at my table nowadays. Which is fine.
It was an awesome session nonetheless, once we started playing. Didn't finish the module (Frozen in Time, for DCC) but seemed like a good adventure (although it requires PCs to be a bit foolhardy at times).
In the end, I had something very positive to say about 5e: I ignored spells, some combat rules, and weapon proficiencies while running a DCC adventure for 5e with no previous adaptation... and it went very smoothly. After we started playing the game, everyone had a blast.
In conclusion, 5e might be a bit fiddly for my tastes, but it is a solid game and works well under this kind of OSR pressure!
Friday, August 24, 2018
Anyway, I realized about half my players don't appreciate house rules or share my desire to "fix" all RPGs I play. They want to play the game as written.
Of course, maybe all your players love YOUR house rules! I hope they do! However, it has been a common experience for me both as a player and as a GM to see resistance to house rules.
|This is what many people think about house rules... (source here)|
As a player, I like SOME house rules... while others irritate me. I have also heard of GMs changing the rules so thoroughly as to make a number of character concepts impossible.
For me, house rules are not only a way to make the game better or more balanced but... more interesting! Why not have a Str monk or Int sorcerer?
And, of course, more fun - which is why many of my house rules are meant to make the game simpler.
Finally, house rules are COOL! See the PrinceCon 1978 D&D variant rules. They were creating an improved version of D&D (with three saving throws!) a couple of years after the game was created - to use for a single weekend!
Anyway, I like house rules, but half my players don't.
My solution so far has been this: (most) house rules are OPTIONAL for PCs. So, I create new weapons and feats, but the PCs can use the ones in the books if they prefer. Something like "carrots, not sticks".
I allow people to stay conscious after the first failed death save - they can continue fighting (its their funeral!) or they can choose to drop unconscious as the game dictates.
I give a couple of classes that I find lackluster a small boost (PCs can pick it or leave it), but do not "fix" classes or spells that I find overpowered. I'm not really a fan of feats like Lucky or Sharpshooter, but use what you like! I haven't seem a 5e build that would really ruin games.
If you have a character concept that is a bad fit for 5e, I probably want to give you a boost. If you want optimization, OTOH, I'd say RAW has plenty of options for that already.
I offer critical hits to PCs, but would NEVER impose fumbles (which I find silly anyway).
Rules that mess with damage are generally mandatory (and rare), so don't expect to survive a 100-foot fall too easily in my games. However, I WILL warn you if you attempt to jump from the tower of the castle believing you will fall softly BEFORE you make this decision...
NPCs don't have to play by the same rules, of course. And I'm certainly not restricted by random treasure tables!
RAW is optional for GMs, after all! ;)
Saturday, August 11, 2018
At a first glance, the cleric can look like an "odd duck"* in D&D. You have fighters/mages/thieves that can use combat/spell/skills to defeat their enemies. Thieves are somewhere between fighters and magic-users, with access to some combat capabilities and some spell-casting.
(*BTW, we will disregard the fact that fighters/mages/clerics were the original classes, that the elf is the original fighter/mage, or that the thief class is as old as the paladin - we are looking at this from a mechanical, not historical, perspective, which is also why we're calling the magi-users "mages" etc)
However, the cleric fits perfectly among the other three. Let's see:
- The fighter has the BEST access to weapon, armor, BAB, and HP, and the WORST access to spells.
- The mage has the WORST access to weapon, armor, BAB, and HP, and the BEST access to spells.
These two classes, by themselves, would be enough to play the game. People who like the fighter/mage/thief combination often see the thieves as middle ground... But see, they have VERY LIMITED access to armor, spells. and HP. Of course, they thieves have their own abilities, which make them good attackers (sneak, back-stab) and explorers (climb, find traps, etc).
The cleric, then, fulfills a different role: with more access to armor and HP, and also lots of spells, but mostly focused on DEFENSE rather than offense.
Then you'd have:
- The fighter has the BEST access to combat offense AND defense, and the WORST access to spells.
- The mage has the WORST access to combat offense AND defense, and the BEST access to spells.
- The thief has BAD access to combat defense and spells, but GOOD access to combat offense.
- The cleric has GOOD access to combat defense and spells, but BAD access to combat offense.
Of course, you can also say that the mage is more focused on offense than the fighter (great firepower, less protection), then you have something like this:
Quite elegant IMO!
This is why my retroclone, Dark Fantasy Basic, uses the four "classic" classes rather than OD&D's original three, or fighter/mage/thief.
You can also turn the dials to create infinite combinations - good offense and magic for the elf, great defense and magic resistance for dwarves, etc. Or you can mess with range (clerics have fewer ranged options since they cannot use bows, for example), alignment (clerics tend towards Lawful), XP, etc. In all instances, there seems to be a place for the cleric.
Of course, there are DIFFERENT reasons to dislike the cleric. Delta's D&D Hotspot makes a great case against the class... This is a particular strong point:
As I've said on numerous occasions, it is the cleric class which makes the least overall sense in the context of pulp fantasy, and is the most fundamentally troubling class to be included in Original D&D. Among other multifarious reasons, the armored, adventuring, miraculous man-of-Catholic-faith is simply not a type you see very much in the roots of the genre, if at all. The inclusion really sticks out like a sore thumb in OD&D.
I agree - thematically, the cleric makes little sense.
However, there seems to be a mechanical space for the "defender" type, maybe some type of knight, paladin or war leader, focused on protection/support and strong defenses. Someone like King Arthur, Aragorn, etc. Not exactly "pulp" but within what I expects D&D to be nowadays.
Friday, July 27, 2018
Suggested stat line (inspired by RC and S&W):
Goblin. AC 6 , HD 1d6; Move 30'; Atk Spear (1d6); Save F0; Morale 7.
Ogre. AC 5 , HD 4d10; Move 30'; Atk Club (1d6+2); Save F4; Morale 7.
AC: as written [in brackets].
Move: as written [in brackets, if there are two numbers].
HP: maximum possible HP. If the HD indicates a single number instead of a type of die (for example, 3 inttead os 3d6), multiply HD by a number based on size: 6 for goblins, 8 for human, 10 for ogre/troll, 12 for giants/dragons, 20 for gargantuan creatures.
Damage: always deal maximum damage.
Bonus to hit: equal to HD.
Saves: bonus equal to the number indicated in two saves, as appropriate; usually Strength & Constitution for F, Wisdom & Intelligence for M, Dexterity & Intelligence for T, etc. Otherwise, halve the bonus.
A monster that saves as F8 would have +8 bonus to Strength and Constitution saves, +4 bonus otherwise.
The goblin mentioned above would have a 6 HP and deal 6 damage per attack, while the ogre would have 40 HP and deal 8 points of damage per attack.
|by Russ Nicholson|
And this is the (horribly difficult and convoluted) way I used to reach these conclusions:
I'm turning my old one page dungeon into a 30ish-pages module, and since I play both 5e and B/X, I was considering making it compatible with both (plus Dark Fantasy Basic, which is supposed to be compatible with B/X anyway).
I'm playing with the idea of having a single line of stat for BOTH systems. Thought it might be possible with some abbreviations and conversion. So I started playing with this idea.
Not that such type of conversion is necessary: we already have plenty of monsters for BOTH systems, and the easiest way to "convert" is finding a similar monsters. The thing is, I LIKE playing with numbers. So here we go!
I'll usa a goblin, an ogre and a large/adult red dragon as examples, just because. The numbers are from the RC, and the math is mostly done in my head as I write so... let me know if I got it wrong.
This one is actually not hard: just use an abbreviation such as "as leather" or "as plate+6", or even "as leather+1". Of course, armor and shields function differently in each edition - armor and shields provide a bigger bonus in 5e, which makes things more difficult.
Converting the actual numbers isn't hard either: jus subtract RC AC from 19 and you're good to go. The results are far from perfect:
|AC||RC||5e (RAW)||5e (19-original)||5e (armor based)|
|Red Dragon||-3||19||22||Plate+6 (24)|
One problem is that that dragons have AMAZING AC in old school D&D - a purple worm (also 15 HD) has AC 6 ("scale"), for example (9 points worse than the dragon), while in 5e the AC is almost the same (18 versus 19).
Another problem is that in 5e armor scales with CR, which doesn't happens as much in the RC. So, the purple worm has the same AC as a Minotaur in the RC, but in 5e, it beat the Minotaur 18 against 14.
Sigh. Let's just stick to the formula for now. So, the dragon has AC -3 , if we're using S&W notation.
Hit Dice (and "THAC0")
Here is the crux of the matter: 5e doesn't use HD in exact the same way as TSR-D&D. But it's there - and its useful. Let's compare:
|HD||RC (d8)||5e (RAW)|
|Ogre||4 + 1 (L)||7d10+21|
|Red Dragon||15 (L)||19d12+133|
As you can see, 5e numbes are heavily inflated when compared to RC. The number of HD is nearly doubled (the 5e dragon has 19 HD, but lots of extra HP).
However, HD is used in two ways in the RC: to generate hit-points and to-hit bonuses (equivalent to "THAC0").
HP in 5e is WAY higher than the RC, specially at higher levels. However, if we break from the RC conventions and make HP vary with size like 5e suggests (say, 1d6 for goblins, 1d8 for humans, 1d10 for ogres, 1d12 for adult dragons, 1d20 for ancient dragons and purple worms), we could use the HD listed in the RC but giving MAXIMUM HP to each creature. So, the 15 HD dragon would have 180 HP (15x12). With the added AC, he would be a bit tougher than the 5e one, as long as we improve his saves, too.
|HP||RC||5e (RAW)||5e (our formula)|
"To-hit" can simply be based in HD, like many OSR enthusiasts suggest: 5 HD means +5 to-hit etc.
|"To-hit"||RC||5e (RAW)||5e (our formula)|
If a "Save DC" is needed, we will use the same number, plus 10.