Traits

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.

Actions

Shock: Melee Spell Attack: +4 to hit, reach 5 ft., one creature. Hit: 9 (2d8) lightning damage.

Invisibility: The will-o’-wisp and its light magically become Invisible until it attacks or uses its Consume Life, or until its Concentration ends (as if concentrating on a spell).