Specter

Medium undead, chaotic evil

Armor Class 12
Hit Points 22 (5d8)
Speed 0 ft., fly 50 ft. (hover)

Damage Resistances acid, cold, fire, lightning, thunder; bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities necrotic, poison
Condition Immunities charmed, exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained, unconscious
Senses darkvision 60 ft., passive Perception 10
Languages understands all languages it knew in life but can't speak
Challenge 1 (200 XP)

Incorporeal Movement. The specter can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.
Sunlight Sensitivity. While in sunlight, the specter has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Actions

Life Drain. Melee Spell Attack: +4 to hit, reach 5 ft., one creature. Hit: 10 (3d6) necrotic damage. The target must succeed on a DC 10 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the creature finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.