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

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

Haste. Until the spell ends, Zaenna's speed is doubled (included in the stat block), she gains a +2 bonus to AC (included in the stat block), has advantage on Dexterity saving throws, and gains an additional action on each of her turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or [Tooltip Not Found] action. When the spell ends, Zaenna can't move or take actions until after her next turn, as a wave of lethargy sweeps over her.

Ike’s Spells.

Death Ward: The first time Zaenna would drop to 0 hit points as a result of taking damage, she instead drops to 1 hit point, and the spell ends. If the spell is still in effect when Zaenna is subjected to an effect that would kill her instantaneously without dealing damage, that effect is instead negated against Zaenna, and the spell ends.
Freedom of Movement: Zaenna's movement is unaffected by difficult terrain, and spells and other magical effects can neither reduce her speed nor cause her to be paralyzed or restrained. Zaenna can also spend 5 feet of movement to automatically escape from nonmagical restraints, such as manacles or a creature that has her grappled. Finally, being underwater imposes no penalties on her movement or attacks.
Heroes Feast and Motivational Speech: Other than what is already included in the stat block, the first time Zaenna is hit by an attack, she gains advantage on the next attack roll she makes. Additionally, she has advantage on Wisdom saving throws.

Sneak Attack (1/Turn). Zaenna deals an extra 14 (4d6) damage when she 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 Zaenna that isn't incapacitated and Zaenna doesn't have disadvantage on the attack roll.

Multiattack. Zaenna makes two shortsword attacks. She has an additional action (single attack) due to haste.

Shortsword. Melee Weapon Attack: +8 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: +8 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.