Mukotai Ambusher

Ninjutsu's whole trick is converting connected damage into a fresh threat: swing with a cheap evasive body, and once the declare blockers step has passed and the attacker is officially unblocked, pay the activation to return it and drop the ninja in its place, tapped and already attacking through the defenses. The returned attacker leaves before combat damage, so you are not double-dipping on the hit; what you are doing is trading a small unblocked creature for a 3/2 that lands its blow this turn. Lifelink is the payload that makes this particular swap worth it. Where most ninjas cash an unblocked hit into cards or a triggered ability, this one banks life, and a chain of ninjutsu activations turns a stable tempo lead into a widening life cushion: bounce a one-drop, land this for the lifelink strike, and next turn slot something over the top of it. The activation cost keeps the sequencing honest, since you are paying to recommit a body you already spent rather than getting the swing for free. As an artifact creature it also feeds the equipment and sacrifice-value shells a rat ninja tends to live in without asking the deck to bend around it. It is a role-player rather than a headliner: the lifegain-slanted option in a mechanic black shares with blue, built for aggressive tempo shells that want their unblocked hits to buy staying power alongside damage.