Barrenton Medic

The genius of this design is that its two abilities solve each other's problem. A damage-prevention shield that taps to fire once is a fine roadblock, but it stops only one point per activation; the second line lets it refund its own tap by paying a -1/-1 counter, turning a 0/4 wall into a reusable prevention engine that fogs four points of incoming damage across a turn before the body collapses. The counter is the meter on the machine: every untap shaves a point of toughness, so the wall comes with a built-in fuse, and the puzzle is how much damage you can soak before the medic kills itself. That self-inflicting cost is also the open door, since shrinking a creature you control is a resource in the right shell rather than a drawback, and a deck that wants to seed its own creatures with counters can recoup the loss or feed it into something hungry for the decay. On its own it is a defensive specialist: a patient, repeatable point of prevention aimed wherever it is needed, equally happy blanking a swing or babysitting another creature through combat. The interplay between a self-untapping engine and a self-decaying clock explains the unusual stat line; this is a 0/4 and not a 0/1 because the toughness is the ammunition.