Diseased Vermin

A snowballing damage engine hidden inside a 1/1 with no evasion, and the disguise is the whole problem. The clock starts the moment it connects: the first hit deals its single point of combat damage and plants an infection counter, and from then on the rat pings that specific opponent at the beginning of each of your upkeeps for damage equal to its accumulated counters. The structural move is that the counters track on the creature itself, so the recurring upkeep trigger becomes the real threat rather than the combat step. But the engine only scales if you keep connecting: counters are added on combat damage, not on the upkeep ping, so the moment it stops attacking the upkeep damage flatlines at whatever total it had reached. That forces a brutal bargain, since attacking with a 1/1 to grow the counter means feeding it into any blocker, any one-toughness sweeper, any spot removal, all of which erase the body and every counter riding on it at once. That fragility is the balancing friction: a design that demands a long, undisturbed game from a creature with no resilience to offer, and the counters live nowhere but on a thing that dies to a stiff breeze. It is one of black's early "you got hit, now you suffer" experiments, an attrition engine rather than a tempo play, slow inevitability that reads as menacing in the abstract and folds the instant the opponent spends a single removal spell.