You embody the mantis in your fighting techniques.

Ambush Predator

When an enemy enters your melee range, you can use a reaction to make an attack of opportunity against them. You can expend a ki point to become invisible until the end of your next turn, or until you make an attack or cast a spell.

Seize and Devour

At 6th level, You can take two reactions instead of one each round. You also gain the ability to leech ki from your fallen foes. When you reduce a hostile enemy to 0hp, you regain 1 ki point. Additionally, your checks made to grapple are made with acrobatics in place of athletics.

Merciless

Starting at 11th level, when you use a ki point to turn invisible, it no longer ends when you make an attack or cast a spell. When you successfully grapple a target, you may make another grapple check contested by their own. If you succeed, they are restrained.

Punishment

Starting at 17th level, when an enemy misses you with a melee attack, you can use your reaction to make one unarmed strike with advantage. Additionally, this attack is a critical hit on a roll of 19 or higher.