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

Sneak Attack. Once per turn, the footsoldier deals an extra 10 (3d6) 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 footsoldier that isn't incapacitated and the footsoldier doesn't have disadvantage on the attack roll.

Dash Attack. If the footsoldier moves at least 20 feet and then hits with a vicious sickle attack, then the target takes and extra 4 (2d4) damage. If the target is a medium or smaller creature, then it must DC 13 Strength saving throw or be knocked prone.

Innate Spellcasting. The Yiga Clan are trained in a variety of spells that allow them to easily ambush their targets, and escape with out notice. The yiga footsoldier's innate spellcasting ability is Charisma (save DC 12, +5 to hit with spell attacks). The yiga footsoldier can innately cast the following spells, requiring no material components:

At will: Disguise Self, Misty Step

2/day: Teleport (self only)

Vicious Sickle. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) slashing damage.

Duplex Bow. Ranged Weapon Attack: +5 to hit, range 150/600 ft., one target. Hit: 12 (2d8 + 3) piercing damage.