Will-o'-Wisp

The monster can't wear or carry anything.

The monster sheds Bright Light in a 20-foot radius and Dim Light for an additional 20 feet.

The monster can move through other creatures and objects as if they were Difficult Terrain. It takes 1d10 force damage if it ends its turn inside an object.

The monster and its light have the Invisible condition until the monster's Concentration ends on this effect, which ends early immediately after the monster makes an attack roll or uses Consume Life.

Melee Spell Attack: +9 to hit, reach 5 ft., one target. Hit: 2d8 lightning damage.

Constitution Saving Throw: DC 10, one living creature the monster can see within 5 feet that has 0 Hit Points. Failure: The target dies, and the monster regains 3d6 hit points.