D&D 5E Do any creatures not eat/sleep? What about familiars?

[seebs]

I can't find anything specific on this. Monster manual says there's no specific rules for the creature types themselves. Find familiar makes your familiar a celestial, fey, or fiend (your choice). When a chain-pact warlock casts find familiar, they can also pick additional forms, like sprite. Can they make the sprite into any type they want? Does any of that have any impact? Does the sprite need to sleep or eat? I currently assume they do, but the ability to desummon and resummon suggests that there's some weird stuff going on.

(Side note: I also assume you actually need line-of-effect and line-of-sight to summon your familiar, not just "any unoccupied space within 30'.)

 

[Li Shenron]

I think it should always be about the backstory/concept you want to have for a creature in your fantasy world.

Typically, I assume that creatures that aren't "alive" in the same sense as mortals are, don't need to do the very things that are required to mortals in order to stay alive, such as eating, drinking, sleeping and even breathing, tho they might often being capable of doing so if they want. This includes fiends, celestials, other outsiders, undead, constructs and elementals.

On the other hand, some of them might need other things to stay "alive" (reiterating that this means something different for them compared to mortals). Elementals might need to absorb/replenish the same substance they are made of, fiends (celestials) might need to do or cause evil (good) often enough or fade out of existence, some undead or fiend may feed on souls, construct may need to recharge their "batteries"...

But all this is IMHO part of the story first and foremost, and the DM is in charge of the story, not the Monster Manual.

 

[the Jester]

Look in the actual creature write-ups. Those that don't need to breathe, eat, sleep or drink spell it out in the flavor text, usually in a section called "Undead Nature" (or Construct Nature, or whatever).

 

[PnPgamer]

Or you could go and check out dnd 3.5 creature types
Here i even give you the link
http://www.d20srd.org/srd/typesSubtypes.htm#types

Under each type there is "traits" section. Check the last pip and there you go.

Do note that while no undead need not to eat, vampires experience the craving for blood, ghouls like to eat corpses, shadows want to drain your bodlily strength etc.