Caligrosto

Incorporeal Movement. The caligrosto 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.

Fiendish Shade. When the caligrosto is not Invisible, it shape-shifts into a mirror image of the last creature it damaged (no action required), although this resembles a fiendish incarnation of the creature duplicated. A caligrosto can only duplicate the image of a creature capable of wielding a Slashing weapon, and it remains Medium size no matter what size the original creature was. The caligrosto has Advantage on attack rolls made against a creature it is duplicating.

Magic Resistance. The caligrosto has Advantage on saving throws against spells and other magical effects.

Superior Critical. The caligrosto's attack rolls are a Critical Hit on a roll of a 17 or higher on the d20.

Multiattack. The caligrosto makes two Greatsword attacks.

Greatsword. Melee Attack Roll: +8, reach 5 ft. Hit: 12 (2d6 + 5) Slashing damage plus 3 (1d6) Necrotic damage.

Withering Touch (Invisible Only). Wisdom Saving Throw: DC 17, one creature within 5 ft. Failure: The target's Strength score is reduced by 1d6. A creature whose Strength score is 0 dies.

Inhabit. Charisma Saving Throw.: DC 17, one Slashing weapon the caligrosto can touch. Failure: The caligrosto inhabits the weapon. A nonmagical or nonsentient magic weapon is automatically inhabited. Success: The weapon is immune to the caligrosto's Inhabit ability.

Once a caligrosto inhabits a weapon, it can enter or leave the blade by expending 5 feet of movement as long as the blade is within 5 feet of it. While possessing a weapon, the caligrosto's Speed is 0 and it cannot make attacks, nor can it be detected by most effects that detect creatures (such as See Invisibility or Locate Creature). Detect Evil and Good reveals that the inhabited weapon has that alignment, but not that a demon lurks inside. Truesight reveals the weapon to be seething with coils of what appears to be mist flecked with lightning. The caligrosto can still observe the world around it, but its ability to interact with the world is limited to its telepathy.

Vanish. The caligrosto gives itself the Invisible condition if it is not wielding a Slashing weapon, or ends that condition on itself.

Parry. Trigger: The caligrosto is hit by a melee attack roll while holding a weapon. Response: The caligrosto adds 2 to its AC against that attack, possibly causing it to miss.