Ukkima, Stalking Shadow

The unblockable clause is the setup; the leaves-the-battlefield trigger is the payoff, and the trick is that the two abilities were built to be fired repeatedly rather than kept on the board. A 2/2 that can't be blocked chips in a couple of points each turn, but the real value comes from bouncing, blinking, or sacrificing it: every time it leaves, it drains for its power and refunds you the same amount of life, so the body becomes a reusable Blood Artist-style trigger that also happens to be a clock. That reframes the design goal. Most evasive beaters want to stay on the battlefield swinging; this one wants to die on your terms, over and over, turning any recursion engine into a Reservoir of incremental drain. Pairing it with a way to grow its power multiplies both halves of the swing at once, since the same X governs the damage and the lifegain. The Partner-with clause quietly tutors up its counterpart, so the pair arrives as a package rather than a lucky draw. What holds the design together is that the damage only ever hits a single player, keeping it a targeted assassination tool rather than a board-wide finisher, and the two-color cost keeps it in the shell that most wants to abuse enter-and-leave loops.