I was about to insert a Wereraven (from Van Richten's Guide to Ravenloft) into one of my 5e D&D campaigns, until I read the stat block more closely.
The NPC in question isn't really meant as a combat challenge, but more of a roleplaying challenge, so I almost rolled ahead with this without looking too closely at the stats. Glad I noticed it now, while I still have time to scour the internet for a different version of the Wereraven, or make up my own custom stats for this NPC.
The stat block in Van Richten's is weirdly retro. It feels like it is from a completely different edition of the game. Here's all the stuff that seems out of place:
Lack of Immunity: Most lycanthropes in 5e have "Immunity to bludgeoning, piercing, and slashing from nonmagical attacks not made with silvered weapons". The Wereraven does not. Instead it has:
The Only Lycanthrope with Regeneration: "The wereraven regains 10 hit points at the start of its turn. If the wereraven takes damage from a silvered weapon or a spell, this trait doesn’t function at the start of the wereraven’s next turn. The wereraven dies only if it starts its turn with 0 hit points and doesn’t regenerate."
It is identical to what a Troll has in 5th Ed, just with silver and magic as it's weakspots instead of fire and acid. So it's not entirely unprecedented for a monster, but it's really unlike any of the other lycanthropes in 5e. it is like lycanthropes in earlier editions, from back when Regeneration was a much more common effect. It seems like the authors of Van Richten's Guide just converted an old 2nd Ed stat block directly, without looking to see how the current version of lycanthropy plays at the table.
10 HP per turn is more than 100 times better than a Ring of Regeneration (heal 1d6 every 10 minutes) or Ioun Stone of Regeneration (heal 15 every hour). You might be thinking "yes, but those are magic items a PC might get their hands on"... but if I were to use this Good-Aligned Wereraven as-written, I think my PCs would feel a strong temptation to get themselves bit. Regeneration 10 would be huge on a PC.
The only downside to lycanthropy in this edition to prevent PCs from seeking it out is this: if you catch lycanthropy your personality and alignment transform to that of the species that bit you, and the GM is free to turn your character into an NPC when that happens... but if our party's Lawful Good Paladin contracted wereravenry and became... Lawful Good? Well, I think their player would be pretty miffed at me taking their character away for that, and rightly so.
I will say that the default 2014 Lycanthrope Damage Immunity rule makes Lycanthropes very dangerous if you don't have an appropriate weapon or spell, but keeps the fights reasonably short if the whole party does have access to such features (and usually they all do by the time you're high enough level to fight were-critters). So it makes you feel like well-equipped competent heroes, and explains why the townsfolk needed you to save them. I'm glad they went with immunity for these monsters (generally) instead of regeneration, which sometimes makes fights drag on forever.
Useless Mimicry: The wereravens have a Mimicry ability that seems entirely pointless. They can duplicate nearly any sound, which has cool roleplay possibilities, but they are hamstrung by not using the current editions typical rules for illusions, tricks or buffs. Seeing through an illusion in 2014 edition PHB usually involves the person using an entire Action to make an Intelligence (Investigation) check. You basically don't get to roll unless the player has some reason to wonder if things aren't what they seem, and is willing to waste a turn gambling that they'll roll well. (2024 PHB is basically the same, but they standardized this into the Study Action, which means there's a couple subclasses who can do this as a Bonus Action instead of burning their turn.)
Instead of following those standards, this mimicry ability can be detected with a Wisdom (Insight) check vs DC 10, with no mention of it taking any other resource (not Action, Bonus Action, Reaction, etc).
In 5e, the target numbers for such things are usually 8 + Proficiency Bonus + Spellcasting Modifier. So for a CR 2 monster with all above-average mental traits like this one, I'd expect a DC in the 11 to 13 range, not 10. And since it didn't cost an Action, chances are the whole party is going to want to roll, so somebody's bound to pass it. Even if you do the Insight equivalent of "Passive Perception" so that you're not alerting the table to the fakery by having someone roll... well that DC 10s not enough to fool basically anyone. You'd need a below-average Wisdom and be untrained in order to fail that Passively. (Not that Passive Insight is a thing in 5e either, but my point is that even swapping what skill is being tested to Perception and avoiding the die roll still doesn't salvage this useless ability.)
EDIT: And lastly, it seems odd that a creature with a Mimicry ability doesn't have ranks in Deception skill. I know the GM rarely rolls such skills, but thematically it sure would make sense for this ability to involve such a roll, and/or to give the wereraven Advantage on Charisma (Deception) checks made to mimic a voice or fool someone about what they heard. Just a thought.
ANOTHER EDIT: I know I already "lastly", but I just noticed that the Language entry says "Common (can't speak in raven form)". That parenthetical clause sure makes the existence/logic of the Mimicry ability even more questionable, doesn't it? I know it's actually like that to be more consistent with the other 5e lycanthropes, but I find it funny and a little frustrating that they stick to the template on this one issue where it would actually make sense to divert, but then go way off the gameplan on more critical stats.
ONE MORE EDIT: I eventually figured out why the DC is 10. It's because they just copy-pasted the Mimicry entry from the normal Raven stat block. That basic Raven is CR 0 and Charisma 6, instead of Wereraven's CR 2 and CHA 14. It would be a very unusual circumstance if a normal Raven were using its mimicry to trick someone or lure them into an ambush, so it didn't need much in terms of rules.
