Invisible stalker

An invisible stalker is an elemental assassin, summoned from the Elemental Plane of Air to a single purpose given by its master.

Description
The creature is native to the Elemental Plane of Air but can be summoned into the material plane. The stalker is entirely loyal to its master, following their commands for the duration of the spell that forces its servitude.

As an assassin, a stalker always knows where its target is and no matter how far they are from each other, provided they are on the same plane of existence. It remains entirely invisible when they attack.

Appearance
The invisible stalker is the approximate shape of a human and stands around eight feet tall. Made entirely of air, however, it is completely invisible. Even magic which reveals invisible, such as see invisibility, shows only a vague outline.

Abilities
The following is drawn from the Monster Manual:


 * Damage Resistances: Bludgeoning, Piercing, and Slashing from Nonmagical Attacks
 * Damage Immunities: Poison
 * Condition Immunities: Exhaustion, Grappled, Paralyzed, Petrified, Poisoned, Prone, Restrained, Unconscious

Attacks:


 * Multiattack: The stalker can make two slam attacks during it's turn.
 * Slam: Attacks with a melee weapon +6 to hit, reach 5 ft., one target. If hits: 2d6 + 3 bludgeoning damage.

Known stalkers
Two invisible stalkers were summoned by the Briarwoods and attacked the Greyskull Keep, most likely to eliminate Desmond, Vox Machina's information source of the Briarwoods' operations in Whitestone.

The Mighty Nein encountered an invisible stalker within the Radiant Stair of the King's Cage.