Ugin's Conjurant

The clever part is what the counters do double duty as: they set the body's size on entry, but they also function as a damage-absorbing reserve that gets spent rather than a toughness that gets checked. When damage comes in, the whole amount is prevented and that many counters vanish at once: a three-point burn spell strips three counters in a single removal, not three separate shavings. A creature made entirely of counters that trades those counters to eat damage is a genuinely different object from a vanilla X/X. That mechanic ties it to the broader family of creatures whose whole identity is +1/+1 counters: it wants proliferate, it wants counter-doublers, it wants anything that refills the pile it keeps spending. Restock the reserve and the same creature that soaked a burn spell last turn is back to full and ready to absorb another. The tension the design resolves is that a counter-payoff creature normally sits there being a passive target for counter synergies; this one turns its own counters into an active defense, so the pieces you were already running to grow it also keep it on the table. The catch is unforgiving: the prevention only fires while a counter is present, so if the incoming damage removes the last counter, toughness hits zero and it is put into the graveyard as a state-based action. There is no scratched-and-shrinking survivor at the bottom of the pile: the counter reserve is the only thing standing between the body and the yard, which makes the whole engine a race between how fast you refill and how fast the board tears down.