Legendary Resistance (3/Day). If Zaknafein fails a saving throw, he can choose to succeed instead.

Assassinate. During its turn, the assassin has advantage on attack rolls against any creature that cannot see or sense him. Any hit the assassin scores against a surprised creature is a critical hit.

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

Sneak Attack. Once per turn, the assassin deals an extra 14 (4d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the assassin that isn't incapacitated and the assassin doesn't have disadvantage on the attack roll.

Shadow Movement. While in shadow the assassin's movement doubles

Reaper Scythe. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 6) piercing damage, and the target must make a DC 16 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Nightgale Longbow. Ranged Weapon Attack: +12 to hit, range 150/600 ft., one target. Hit: 8 (1d8 + 6) piercing damage, and the target must make a DC 16 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Shadow Strike. If the assassin is within shadow and within 10 feet of a target, the assassin may leap from the shadow and strike once with Reaper Scythe. Striking this way causes the same effects as if the target could not see or sense him as long as the target doesn't have blindsight or truesight

Shape change. While immersed in shadow, Zaknafein can alter his appearance to perfectly mimic any humanoid creature he has seen before (this includes their voice). This disguise cannot be detected by magical means but can be seen through by magical means.

Tools of the Trade. (Recharge 3) The assassin may cast one of the following spells, Blur, Mirror Image, Silence, Disguise self, or scrying

Slip into Shadow. (Recharge 2). While standing in a shaded or dark area, the assassin may slip into the shadow

Shadow Shackles. (Recharge 3) While immersed in shadow, Zaknafein can appear beneath a creature and attempt to pull them halfway into the shadowed ground. The creature must make a DC 18 Dexterity Saving throw or be restrained

Retreat To Shadow. (Recharge 2) After being struck my an attack, the assassin jumps 5ft away from all hostile creatures (This movement doesn't provoke opportunity attacks) and if this space is within shadow the assassin slips into it.

The assassin has 3 legendary actions that refresh at the beginning of his turn

Last Resort (Actions 3). Dipping into the shadow and forming an array of choice weapons that strike out within a 20 ft cone. Creatures in the area must make a DC 18 Dexterity Saving throw. Creautes within the first 10 feet take 40 (10d8) piercing, creatures outside of the first 10 feet take 24 (6d8) piercing. Creatures in all ranges take half damage on a successful save

Expertise. (Actions 1). The assassin can make any action that he normally could in the actions list as a legendary action.