Will-o'-Wisp

Ephemeral. The will-o'-wisp can't wear or carry anything. In addition, it adds its WIS modifier to its AC (included above).

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.

Undead Nature. The will-o'-wisp doesn't require air, food, drink, or sleep.

Undead Resilience. The will-o'-wisp is immune to poison damage, to exhaustion, and to the poisoned condition.

Multiattack. The will-o'-wisp makes two Shock attacks.

Shock. Melee Spell Attack: +5 to hit, reach 5 ft., one target. _Hit:_ 10 (2d6+3) lightning damage.

Invisibility. The will-o'-wisp and its light magically become invisible until it attacks or uses its Beckon, or until its concentration ends (as if concentrating on a spell).

Beckon. The will-o'-wisp pulses its lightly gently toward one creature it can see within 30 feet of it. The target must succeed on a DC 13 WIS save or use its reaction to move up to its speed toward the will-o'-wisp by the most direct route. It doesn't avoid opportunity attacks or damaging terrain when moving.

Consume Life. When a creature the will-o'-wisp can see within 15 feet of it is reduced to 0 HP, the will-o'-wisp can consume some of that creature's fading life. The will-o'-wisp gains 7 (2d6) temporary HP, and the creature has disadvantage on the next death save it makes before the end of the wisp's next turn.