Will-o'-Wisp

Will-o'-Wisp Tiny undead, chaotic evil 2 450 xp

Armor class 19
Hit points 22 (9d4)
Speed 0 ft., fly 50 ft. (hover)

STR 1 (-5)
DEX 28 (+9)
CON 10 (0)
INT 13 (+1)
WIS 14 (+2)
CHA 11 (0)

Damage Resistances: acid, cold, fire, necrotic, thunder, bludgeoning, piercing, and slashing from nonmagical weapons

Damage Immunities: lightning, poison

Condition Immunities: exhaustion, grappled, paralyzed, poisoned, prone, restrained, unconscious

Senses: darkvision 120 ft., passive Perception 12

Languages: the languages it knew in life

Challenge: 2 (450 xp)

Strahd Zombie

Actions

Consume Life.As a bonus action, the will-o'-wisp can target one creature it can see within 5 feet of it that has 0 hit points and is still alive. The target must succeed on a DC 10 Constitution saving throw against this magic or die. If the target dies, the will-o'-wisp regains 10 (3d6) hit points.
Ephemeral.The will-o'-wisp can't wear or carry anything.
Incorporeal Movement. The will-o'-wisp 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.
Variable Illumination.The will-o'-wisp sheds bright light in a 5- to 20-foot radius and dim light for an additional number of feet equal to the chosen radius. The will-o'-wisp can alter the radius as a bonus action.