How to convert a 4e boss to the 5e system?

Question

I'm soon to be taking the step into my first time as a DM for a group I have played with for some time as a player. I have a few ideas for the adventure I'm going to run, but I find myself stumbling when it comes to creating the final boss in an undead-centric homebrew 5e campaign. The boss I have in mind would be Doresain, King of Ghouls, but the only thing I have been able to find is a 4e version with the old stats system.

What would be the best way to go about bringing this boss forward from the older edition? Finding a way to mix and match existing abilities of other boss-tiered enemies to try and recreate the old enemy? Or, instead, to create a homebrew version on my own from scratch and attempt to playtest it solo until it's beatable? Do you have any recommendations for the stats/ abilities that could make a good 5e version of this character either way?

Answer 1

Conversion is hard.

Converting characters/monsters between editions is hard. Converting between 4e and 5e is especially hard. One of the primary focuses of 4e, if not the the primary focus, was tactical combat, so 4e has a lot of special mechanics to support that style of play. Because 5e sort of supports tactical combat but certainly doesn't emphasize it, 5e lacks equivalents of a lot of 4e's mechanics.

Any 4e monster is going to have a lot of abilities that can't be easily translated to 5e because the corresponding mechanics simply aren't there, or have changed radically. For example, hit points and AC/attack bonuses scale very differently between the two editions, and that's without getting into harder things like changes to conditions or saving throws.

Try adapting an existing monster instead.

Creating a new homebrew monster can also be pretty difficult, particularly for GMs who don't have a lot of experience with the system. It's much easier, instead, to find an existing published monster that is mechanically a good fit, and simply describe it as the monster you want. For example, you could find the stats for an owlbear and instead describe it as an armored knight, talking about his sword when you roll claw attacks, etc. You can still tweak the mechanics as needed of course, but at that point you're making minor adjustments to something that someone who was more familiar with the system built, rather than trying to built it from scratch yourself, which can be overwhelming.

Answer 2

I have been DMing since 1983, and am currently using the 5e rule set. I use resources from all versions of D&D. For 4e monsters, look up the PC proficiency bonus in the 5e PHB (page 15) for the monster's Level (4e monsters have no CR) and subtract it from AC, effect save DCs, and attack bonuses and damage bonuses. Replace feature stats with those from the closest 5e spell. Leave those huge HPs! Recalculate CR using the DMG custom monster table (page 274). Enjoy your gnarley BBEG!

This technique works for some oversized 3.5e monsters; just use the number of hit dice in place of monster Level.