Colfenor's Urn

A reanimation engine disguised as a counting puzzle. Most graveyard-recursion artifacts of its era either paid a flat cost per creature or asked for an activation; this one runs entirely off triggers, demanding instead that you stockpile bodies before it pays out. The toughness-4-or-greater gate is the structural lever: it locks out chaff and points the card squarely at the fat midrange and finisher creatures whose deaths matter most. The exile-then-return loop also sidesteps the usual reanimation tax, since it never asks for mana to bring the creatures back, only patience and a graveyard willing to fill with the right size of corpse.

The friction lives in the count. Three exiled cards is the threshold, and until you hit it the urn does nothing but sit there absorbing deaths; cross it and the artifact destroys itself to dump everything onto the battlefield at once. That all-or-nothing payout makes it a slow, telegraphed engine: opponents can read the count, see the wave coming, and try to deny you the third trigger or remove the urn before the end step resolves. Clearing that hurdle hands you a mass return with no individual mana cost attached, a reward best earned by decks that can manufacture creature deaths on demand rather than wait for combat to deliver them.