Assassin devil (dogai)

Assassin's shadow step. As a bonus action the Assassin devil can turn invisible until the end of their turn or until they attack or cast a spell.  

Shadow form. The assassin devil turns into a shadow like form and for the next 1d6 rounds they count as constantly having half cover from all attacks unless in direct sunlight or illuminated by the daylight spell. 

Magic Weapon. The assassin devil's weapon attacks are magical.

Magic Resistance. The assassin devil has advantage on saving throws against spells and other magical effects.

Devil’s Sight. Magical darkness doesn’t impede the devil’s darkvision.

Avoidance. If the assassin devil is subjected to an effect that allows it to make a saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Sneak Attack (1/Turn). The assassin devil deals an extra 15 (5d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 ft. of an ally of the assassin devil that isn’t incapacitated and the assassin devil doesn’t have disadvantage on the attack roll.

Innate Spellcasting. The assassin devil's innate spellcasting ability is Charisma (Dc 17, +9). It can innately cast the following spells, requiring no material components:

At will: dimension door, fog cloud, nondetection, tongues

1/day: teleport

+1 Cold iron longsword. Melee Weapon Attack: +13 to hit, reach 5 ft., 1 target. Hit: 20 (2d10 + 10) slashing damage and the damage is doubled against fey.