Can the Animate Dead spell be cast on a zombie?

Question

One of the players in my game is a Death Domain cleric and enjoys having a small army of zombies accompany him. We had come to a situation where it is not plausible for him to keep the zombies with him for the 24-hour period, but he spent the change (on a government writ) to get them locked up until his return, so he can try to regain control over his minions.

Is it possible to cast Animate Dead on a Zombie and have the spell work as normal? Is a zombie considered a corpse, technically?

Also, if you say that it should work in theory, here comes the sticky part. He also wants to use this spell on a Mummy Lord (that he doesn't know is a Mummy Lord, yet). Does it simply not work, since it's an undead creature and not a corpse?

Answer 1

From my understanding of the Rules as Written, once you lost control over a Zombie (or Skeleton) that you raised from the dead using Animate Dead, casting the spell again does not give you control again.

Note that killing the zombie/skeleton does not give you a new pile of raw material that you can re-raise. This is because only humanoid can be animated. The bones and flesh of an undead is considered to be undead, not humanoid. This was clarified in the Sage Advice Compendium (thanks to V2Blast's comment for pointing that out). (Note: this paragraph was updated; the previous version said that piles of bones and flesh from undead could be re-raised.)

As for the Mummy, you need to use the Create Undead with a spell slot of level 9, and that only works with regular Mummies, not Mummy Lords. The Create Undead spell also gives the Cleric the ability to reassert control over undeads. It is not clear, though, whether it would be undead you animated yourself or any undead. Only "re-"assert seems to mean that you had control over them before and thus most certainly means that you would only be able to control undead you created and not some that were created by other clerics.

Answer 2

Animate Dead says:

Choose a pile of bones or a corpse of a Medium or Small humanoid within range.

Zombies are creatures and are neither "a pile of bones or a corpse", so they are not a valid target for the spell.

Once you have killed the Zombie, it is once again a corpse and can be animated, or even resurrected.

Answer 3

Zombies and skeletons are the creature type undead, not humanoid. The animate dead spell does not target that creature type.

The description of types in the basic rules states:

A monster's type speaks to its fundamental nature.

The rules list the following creature types: Aberrations, Beasts, Celestials, Constructs, Dragons, Elementals, Fey, Giants, Humanoids, Monstrosities, Oozes, Plants and Undead.

The description of the animate dead spell says (SRD v5.1, p. 115; emphasis mine):

This spell creates an undead servant. Choose a pile of bones or a corpse of a Medium or Small humanoid within range. Your spell imbues the target with a foul mimicry of life, raising it as an undead creature. The target becomes a skeleton if you chose bones or a zombie if you chose a corpse (the GM has the creature’s game statistics).

Creature type - beast, humanoid, undead, fey, aberration, celestial, etc. - has been a staple of the rules for several editions. It has many mechanical implications, such as valid targets for a spell.

In comparison, the resurrection spell targets the corpse of any creature. Animate dead targets only the corpse of a Small or Medium humanoid.