A Mob.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.entity.IEntityMob;

IEntityMob extends IEntityCreature. That means all functions available to IEntityCreature objects also are available to IEntityMob.

Check if the mob is preventing a player's sleep

Link to check-if-the-mob-is-preventing-a-players-sleep

The Method requires an IPlayer object.
Returns a bool.

ZenScript
Copy
entMobObj.isPreventingPlayerRest(IPlayer player);