Medium undead,
Armor Class: 10 + the level of the spell (natural armor)
Hit Points: 15 (Ethereal) or 25 (Ghoulish & Bone) + 10 for each spell level above 3rd
Speed:
(Ghoulish & Bone) 30 ft. ft
, fly: (Ethereal) 20 ft. fly ft
Skills: Ghostly Movement (Ethereal Only). The spirit can move through creatures and objects as if they were difficult terrain. If it ends its turn inside an object, it appears in the nearest unoccupied space and takes 1d10 force damage for every 5 feet traveled.
Terrifying Grasp (Ethereal Only). Once on its turn when it hits an enemy with a melee attack, the spirit can force the target to make a Wisdom saving throw against your spell save DC or become frightened until the end of its next turn.
Revive From Bones (Bone Only). When reduced to 0 hp by anything other than a critical hit or bludgeoning, force, or radiant damage, the spirit leaves its bones behind rather than disappearing. As a bonus action, you can revive it at 1 hit point.
Damage Immunities: necrotic, poison
Condition Immunities: exhaustion, frightened, paralyzed, poisoned
Senses: darkvision 60 ft., passive Perception 11
Languages: understands the languages you speak
Actions
Multiattack. The spirit makes a number of attacks equal to half this spell's level (rounded down).
Deathly Chill (Ethereal Only). Melee Weapon Attack: your spell attack modifier to hit, reach 5 ft., one target. Hit: 1d4 + 2 + the spell's level necrotic damage.
Bone Arrow (Bone Only). Ranged Weapon Attack: your spell attack modifier to hit, range 80/320, one target. Hit: 1d6 + 2 + the spell's level piercing damage.
Vile Claws (Ghoulish Only). Melee Weapon Attack: your spell attack modifier to hit, reach 5 ft., one target. Hit: 1d6 + 3 + the spell's level slashing damage. The target must make a Constitution saving throw against your spell save DC or become poisoned until the end of its next turn. If the target is already poisoned, it is paralyzed instead.