Gloom Surgeon

The damage-prevention clause turns this Spirit into a wall that almost never dies in combat: throw any creature at it, the damage vanishes, and the cost is paid in cards milled off your own library rather than in toughness. That last part is the design wrinkle, and it cuts both ways. A 2/1 body that ignores combat damage entirely would be absurd at this rate, so the restriction is self-inflicted: every block bleeds your top cards into exile, capping how long the blocker can stay up and threatening to mill you out if you lean on it too hard. The exile (rather than graveyard) destination matters too, since it shuts off graveyard recursion as a way to recoup those cards. What you get is a blocker priced by your own deck's depth rather than by combat math, which inverts the usual question: instead of "can my creature survive this fight," it asks "how many cards is this fight worth." The body still folds to any direct removal or any noncombat damage, so the prevention is narrowly combat-only and easy to play around once an opponent stops attacking into it. It is a self-limiting answer to ground stalls, a defensive piece whose meter is the cards you are willing to spend keeping it on the table.