Legendary Resistance (2/Day). If Ziki fails a saving throw, she can choose to succeed instead.

Assassinate. During its first turn, Ziki has advantage on attack rolls against any creature that hasn't taken a turn. Any hit Zikiscores against a surprised creature is a critical hit.

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

Sneak Attack. Once per turn, Ziki 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 Ziki that isn't incapacitated and Ziki doesn't have disadvantage on the attack roll.

Change Appearance. Ziki can use her action to polymorph into a Medium humanoid it has seen, or back into its true form. Her statistics, other than its size, are the same in each form. Any equipment she is wearing or carrying isn’t transformed. She reverts to its true form if it dies.

Multiattack. The assassin makes two shortsword attacks.

Shortsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Light Crossbow. Ranged Weapon Attack: +6 to hit, range 80/320 ft., one target. Hit: 7 (1d8 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Clawfoot Wand. (Recharge 5+) Cast Summon Animals as a level 3 spells to summon 4 Clawfoot Raptors 

Unsettling Visage (Recharges after a Short or Long Rest). Each creature within 30 feet of the changeling must succeed on a DC 16 Wisdom saving throw or be frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Cunning Action. Ziki can Hide, Disengage or Dash as a Bonus Action

Reactive Tumble. Trigger: When a hostile creature moves adjacent to Ziki. Move 30 feet, do not trigger attacks of opportunity and attacks against Ziki have Disadvantage until her next turn.

Feather Fall. When Ziki should take falling damage she can use this reaction to not take falling damage.

Ziki can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Ziki regains spent legendary actions at the start of its turn.

Quick Slash. Ziki makes a Short Sword attack at Advantage

Dark Reaver Powder. A creature within 15 feet of Ziki must make a DC 16 Con saving throw or become Poisoned. While Poisoned the creature deals half damage from Strength based attacks. A creature can retry this save at the end of its round. 

Assume Form. Ziki assumes the form of a humanoid creature within 5 feet of her. As long as she stays next to that creature any attack targeting her has a 50% chance of hitting that creature instead.