The Thri-Kreen in the Monsters Manual (page 288) have four arms. The benefit they seem to gain from this is the ability to use a two-handed weapon while wielding another weapon.
Without houseruling anything, a creature with extra hands would just get more hands wherever the rules call for hands. For example, a weapon with the Two-Handed property "requires two hands to use", so you could potentially wield two of those (although, depending on the configuration of the arms, this may not make any physical sense). Grappling and some spellcasting require a character to have a "free hand". A four-handed character would have a free hand even while wielding a two-handed weapon, or even two light weapons and a shield. In fact, it's perfectly within RAW for a Thri-Kreen to grapple an enemy using its free hands while wielding a two-handed polearm.
An obvious question is whether the character would be able to wield four weapons and make four attacks. RAW says no. The rule on Two-Weapon Fighting would still apply as written, and both weapons need to have the Light property, unless you have the Dual Wielder feat.
This rule from the Dual Wielder feat becomes interesting:
You gain a +1 bonus to AC while you are wielding a separate melee
weapon in each hand.
Does that mean you need to wield melee weapons in all of your hands to gain the benefit? As written, it's not clear, but from context (it's dual wielding after all), you'd just need to have weapons in at least two of your hands. The intent is likely that you gain the benefit because you cannot use a shield, so perhaps the rule should be that you have a weapon in two hands and no shield.
Not totally broken
The easiest way to determine if this is any good is usually to compare to other races - so lets go item by item
Ability Score Increase. Your Constitution score increases by 2, and your Dexterity score increases by 1.
+2/+1 is in line with many existing races:
- Elf: +2 DEX / +1 [INT/WIS/CHR]
- Halfling: +2 DEX / +1 [CHR/CON]
- Dragonborn: +2 STR / +1 CHR
This seems to follow the baseline stats of many D&D races.
Size. Skeletons match the height, but are half the weight of humans. Your size is Medium.
Speed. Your base walking speed is 30 feet.
These are fairly standard, although it is worth noting that some races such as Dwarf/Halfling which have relatively strong features are limited down to 25ft base movement. If you decide that the race is perhaps a little strong this is somewhere I would consider adjusting it slightly.
Darkvision. Thanks to your undead nature, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
This is quite standard, but it's also worth noting that not all races have access to this. Aarakocra, Human, and Dragonborn do not (although many do). If we determine this race to be quite strong I would consider removing this small feature, to encourage the character to take the light cantrip or carry a torch.
Body Construction. Because of your relentless undead fortitude your body is capable of detatching and reattaching limbs. After a long rest you can choose one of the following abilities:
- Detach Hand.
- Detach Head.
- Detach Arm.
- Attach Extra Bones.
These seem thematically cool, and mostly not too strong. the Detach spells seem mostly like interesting cantrip-level spells as far as I can tell, and add flavour to the character.
Attach Extra Bones Seems more powerful however, and could be quite the boon to certain character types. Gaining AC is generally a powerful effect, many characters carry a shield for +2AC and this means they lose the use of one hand for combat. Dual wielding or using a Duelist style can add +1AC for certain character types which is decent in many cases. For higher level characters this can mean gaining more than the benefit of a shield for free. For a monk character type specifically (who cannot use a shield) this power could be very broken.
I would likely advise removing the AC component of this spell, or making one (or more) of the following changes as a bigger down side related to the bonus:
- Half movement speed
- Disadvantage on stealth checks
- Disadvantage on dexterity saves
False Appearance. While you remain motionless, you are indistinguishable from a pile of bones.
Pretty cool, if your PC gets a chance to use this it will be pretty fun.
Necrotic Constitution. You have resistance to necrotic damage, and you have immunity to poison damage, the exhaustion condition and the poisoned condition. You also have vulnerability to bludgeoning damage.
Having a resistance is usually quite strong but not unheard of. Dragonborn, Dwarves, and Tieflings all have resistances to one element.
Immunity is very strong mechanically, although poison is not the most common damage type from enemies.
Vulnerability is however quite a large risk factor and may help balance out the strengths here. Thematically you may want to consider also including the radiant damage type as another nerf for this character. I might suggest something like this:
You also have vulnerability to radiant damage, and whenever you receive bludgeoning damage you receive an additional 1d8 bludgeoning damage.
Undead Nature. You skirt the line between life and death, you count as both humanoid and undead when it comes to spell effects and abilities. You can’t and don't need to eat, drink, or breathe.
Also quite strong. In a survival situation not needing to eat could be big, however this depends on your DM and how they handle survival.
The main problem here is not needing to breathe - this means that your PC can go underwater indefinitely, and may be immune to the effects of certain gas effects or spells. This could also be totally useless depending on what kinds of challenges the party faces, so it's situational - but in those certain situations it is very strong.
Languages. You can speak, read and write common and one other language of your choice.
Seems quite standard for many races.
Summary
Overall everything here is either in-line with other races, or slightly stronger, or situationally stronger. As the dungeon master, it's up to you to decide what you are happy with. My suggestion would be to make a few nerfs, but I don't think the character is totally broken and I think you could run with it.
My Suggestion:
Definitely do something about Attach Extra Bones, I think the additional AC is over the line and is probably the only thing that really is too much.
Probably choose at least two (possibly more) nerfs to take some of the advantage to disadvantage:
- Lower the base movement to 25ft
- Remove nightvision
- Give disadvantage on stealth checks (skeleton feet probably make a similar noise to walking in high heels)
- Remove some immunity/resistance, or increase vulnerability/extra damage
- Require the PC to breathe
- Lower the ability score increase by 1
Best Answer
Here's good news: the description of "Werebears" (MM page 207) describes how werebears usually only infect their chosen companions or apprentices with werebear lycanthropy (and then spend time with them to help them control it). So there's precedent in the Monster Manual for characters choosing to accept the "curse" of lycanthropy as a gift.
Here's bad news: the "player characters as lycanthropes" sidebar (also MM page 207) says:
All the sources I can find tell me that kenku are strongly chaotic creatures; wereravens are lawful good. This is a major alignment shift! Kenku might view this as akin to mind-control: yes, it's power, and that's great, but after you do this you wouldn't be you any more.
If a kenku embraced the change and became lawful good, it would be difficult for them to fit in to kenku society. Most kenku are mischievous tricksters and many are criminals, and a lawful good creature might not enjoy interacting with such creatures.
Here's how your DM should feel about a PC doing this: your DM should be very uncomfortable with a character embracing lycanthropy, simply because it's so powerful. Very few of the creatures your group fights will have magical or silvered weapons, so the lycanthrope will be essentially immune to those encounters. Flying also makes you immune to a broad class of encounters (ie, encounters with creatures who can't hit you while you're flying). If you do this, it becomes much more difficult for the DM to design an interesting encounter.
Of course each DM is different. Some DMs might be okay with having this happen, especially if it happens to the whole group at once; other DMs might follow the rules text above and convert the kenku PC into an NPC.
Think about worldbuilding: Leaving aside the question of kenku for a moment, there's an opportunity for worldbuilding here. If being a wereraven is really so great, why doesn't everybody do it?
Maybe everyone does do it, and your group periodically encounters villages that are 90% wereraven/werebear/weretiger/etc.
If not everybody does it, the DM should think about why that is. Maybe the wereraven alignment change is more than just being lawful good; maybe wereravens are fundamentally different (obsessed with shiny objects, opposed to hats) in a way that makes most villagers reluctant to embrace lycanthropy. Maybe villagers are superstitious and biased against wereravens. Maybe there's something else.
But remember: kenku can't read the Monster Manual. In practice, an NPC kenku considering this isn't going to say: "well, the weapon immunity is good, but the alignment change isn't compatible with my rogue skills..." Instead, the conversation will go: "Hey, if you let me bite you and infect you with this disease I'm carrying, you'll grow wings and be immune to weapons! Trust me, this will be great!" Kenku can't really know for sure what downside there might be for accepting this offer, and it's all going to come down to trust.
(And, note: the wereravens you're talking about are from Curse of Strahd, ie, Ravenloft. Ravenloft is absolutely dripping with things that will lure you in with offers of power and then turn you evil. A very learned PC might be able to identify that this particular offer of power doesn't come with crippling drawbacks -- but most PCs that are willing to accept this sort of bargain probably won't last long in the Ravenloft setting.)