D&D 5E Converting Older Edition Adventures to 5E

[DaveDash]

The DMG custom monster rules are very exploitable. It's trivial to create a CR 1/4 creature that can kill Frost Giants with ease. Here are some things that are "free" for a CR 1/4 monster:

Arbitrarily high movement
Teleportation
Ranged attacks as long as they don't deal more than 8 damage on average
An arbitrarily high number of Legendary Resistances
Immunities to an arbitrary number of conditions (exhausted/charmed/stunned/etc.)
Immunity to fire/cold/force/blunt/piercing/slashing/magical weapons/etc., as long as you halve HP to compensate
Arbitrarily high ability scores, as long as they don't increase damage dealt or total HP (INT 24, WIS 24, CHA 24, CON 24 as long as you give it a small base HD)

I forget whether you can get spell immunity for free as well, but 50 Legendary Resistances is pretty sweet already.

In short, the DMG rules are okay-ish as a formula for telling you how much experience a given creature is worth, since you gotta have something, but they're quite bad at telling you how genuinely dangerous a creature with special abilities is. If you create a custom monster, and it isn't just a sack of HP with a melee attack--suppose that it has a ranged Entangling attack and can teleport as a bonus action to snatch entangled prey--it's guaranteed that the DMG guidelines will underestimate its lethality.

On the plus side, the DMG encounter balancing guidelines already underestimate PCs' (potential) lethality, so tricksy monsters against tricksy PCs might actually be a fair match.

As an aside: one of the best advantages a monster can have is looking so much like a weaker monster that it gets underestimated. In my world, PCs benefit from this constantly. They look just like regular, weak old humans. A squad of 12 hobgoblins doesn't run away from three PCs when they see them coming because the hobgoblins assume they will win! If hobgoblins have been warned by the survivor of a previous battle, or if the PC Necromancer raises an army of skeletons, this ceases to be true, and the hobgoblin squad takes the threat as seriously as an enemy platoon (break contact, skirmish at range while waiting for reinforcements to arrive in force--all the things that frustrate PCs).

I've ran about 40 custom monsters now, and if you avoid obvious exploits and stick with the spirit of how monsters are created, it creates exceptionally good monsters that feel challenging at high levels.

My experience simply does not match your theory. I think if anything you over estimate the lethality of certain abilities. Combat simply doesn't last long enough and you generally don't stack a ton of riders on one monster.

Let me tell you players fear "bags of hitpoints" when those bags of hitpoints can do enough damage to kill them in one turn.

Believe me, when I first read the DMG rules, I hated them. I thought they were hard work, inaccurate, and missing so many factors. But after actually using them a lot I have found the underlining assumptions are correct. It really does just come down to how much damage and how quickly you can put it out, and how much damage you can withstand.
Honestly unless you have an action economy advantage a lot of effects are not worth the cost of the action. A creature can teleport around willy nilly but it's not really doing damage while it's doing that, and in three rounds it will be dead. Better just to hit and hit hard.

 

[halfling rogue]

So if 1e modules recommend a character level (say 5-10), is it safe to assume those levels will work for 5e or should 5e levels be scaled up or down?

 

[Wik]

So if 1e modules recommend a character level (say 5-10), is it safe to assume those levels will work for 5e or should 5e levels be scaled up or down?

Mm, I'd suggest that PCs of an equivalent level are going to be more powerful in 5th. That being said, when I convert modules, I keep them at a 1 for 1 ratio, and rejigger encounters to make them adequate for a 5e setting... this often amounts to changing the amounts of monsters encountered.

 

[mflayermonk]

So if 1e modules recommend a character level (say 5-10), is it safe to assume those levels will work for 5e or should 5e levels be scaled up or down?

I would say 5th level 5e PCs are about as powerful as 10th level 1e PCs.
The spellcasters are closer in power but everyone else is far more powerful (Fighters with x7 shield spells, barbarian rage for half damage, rogue sneak attack is less deadly to setup than backstab was).

 

[FormerlyHemlock]

It depends upon what kind of challenge is involved. 5E PCs seem to be substantially harder to kill than AD&D 2nd edition PCs (and therefore I assume also 1e PCs, although I never played 1e) so in melee combat, the levels are roughly equivalent. However, 5E spellcasters are much, much weaker than AD&D spellcasters, especially outside of tactical combat. I tend to think of a 20th level 5E wizard as roughly equivalent to a 9th level AD&D(2) wizard in terms of the scope of his magic and the strategic challenges he can handle. For example, True Polymorph is 9th level in 5E and is basically equivalent to Polymorph Other at 4th level in AD&D, and AD&D's Polymorph Self at 4th level was approximately as powerful as a 5E druid's 20th level capstone in every way but combat power. Magic Jar was a 5th level spell, available at wizard 9, and if you were to convert it to 5E it would probably be 9th level or higher, if that were possible. (Even the severely-restricted 5E Magic Jar is 6th level, and it is inferior to AD&D's Magic Jar in three ways: 1.) destroying the gem when spell ends; 2.) only works on humanoids; 3.) caster usually dies when host body perishes.) There are tons of other examples, from Invisibility to Stoneskin to Fire Trap.

Offhand, the only ways I know of in which 5E wizards are stronger than AD&D wizards are in illusion magic and the Clone spell, which now functions essentially as the 9th level Stasis Clone spell.

In short, if you have a module which is heavy on non-combat challenges, I would not assume that 5E PCs are anywhere close to twice as capable as their 1E counterparts, and they may perhaps be less capable. But for combat, a 1:1 conversion is probably more than fine, and 2:1 might even be doable. Though honestly I would probably just eyeball the encounters after converting the monster stats to 5E.

Final point: a fair fight in 5E (in the sense of a 50% chance of PC death) seems to be approximately CR = PC level. E.g. if you have 4 17th level PCs, then 4 CR 17 creatures like Red Dragons probably have a decent chance of killing half the party. But 5E is calibrated to play at around 1/4 of that level, 1 CR 17 creature per 4 17th level PCs, so PCs rarely ever face a fair fight at most tables. I don't think AD&D was calibrated that way, so expect to see converted AD&D encounters kill lots of PCs, not because the conversion was bad but because AD&D was designed to be harder.

 

[mflayermonk]

However, 5E spellcasters are much, much weaker than AD&D spellcasters, especially outside of tactical combat. I tend to think of a 20th level 5E wizard as roughly equivalent to a 9th level AD&D(2) wizard in terms of the scope of his magic and the strategic challenges he can handle.

In 1e and 2e it was much easier to instadeath a wizard. For example, in Lost Caves of Tsojncanth there was a rock slide and avalanche that both had a really difficult instadeath save for wizards. Or in Shrine of the Kuo Toa, there are these kuo-toa assassins that will also instadeath a wizard. Wizards always knew it could be there day to be instadeathed.
This problem was usually solved by the wizard's player ordering pizza for the group in order to be given a mulligan on the instadeath. Over time, this made the wizard seem overpowered.
However, it was really delivery pizza that was overpowered.

 

[FormerlyHemlock]

In 1e and 2e it was much easier to instadeath a wizard. For example, in Lost Caves of Tsojncanth there was a rock slide and avalanche that both had a really difficult instadeath save for wizards. Or in Shrine of the Kuo Toa, there are these kuo-toa assassins that will also instadeath a wizard. Wizards always knew it could be there day to be instadeathed.
This problem was usually solved by the wizard's player ordering pizza for the group in order to be given a mulligan on the instadeath. Over time, this made the wizard seem overpowered.
However, it was really delivery pizza that was overpowered.

Sure. It was easier to instadeath anybody in 2E. IIRC a 20th level fighter still had a 10% chance of death (petrification) against a low-level monster like a Basilisk. (Yes, you could potentially get turned back into flesh, but even that had a pretty hefty chance of killing you in the process. And if you got resurrected from that, resurrection was not guaranteed to work, and you also lost a permanent point of Con.)

That's why I say 5E PCs are far more durable--instadeath mechanics have been almost entirely removed from the game, and resurrection is much easier, and PCs have more ways to stacking the odds in their favor. The Lucky feat alone probably makes a first-level 5E PC as likely to pass a save vs. basilisk gaze as an 8th or 10th level PC in 2E, and in 5E you don't even have to look at the basilisk unless you're surprised!

BTW, I hold with those who believe that the whole point of save-or-die effects in AD&D was that you should try to avoid ever making those saves. The saving throw was a last-ditch chance to not die when you messed up, not a primary defense. Combat As War. If you play 5E that way you quickly discover that encounter guidelines are far too easy.