Caldera Hellion

Most devour creatures want you to feed them as much as possible and reward you for going wide first; this one punishes that instinct and then quietly fixes the problem it creates. The two abilities do the heavy lifting in sequence. Devour is a replacement effect, not a trigger: as the Hellion enters, you may sacrifice any number of creatures, and it arrives already wearing that many +1/+1 counters. Only after it has resolved onto the battlefield does its enters-the-battlefield trigger fire, dealing 3 damage to every creature, the freshly fed Hellion included. Because the counters were stacked before the trigger goes on the stack, a sufficiently devoured Hellion walks through its own sweep while everything with three toughness or less burns away. The clever part is the fodder. Your natural devour fuel (one-toughness tokens, mana dorks, sacrifice chaff) is exactly what the 3 damage would have killed anyway, so you eat it on the way in and lose nothing the trigger was not already coming to claim. Left unfed, it is a 3/3 for five that almost certainly kills itself the moment it lands, taking the table's small early creatures with it in a one-sided-then-symmetrical wipe that costs you the body. The math, then, runs against the splashy text: with nothing committed and nothing to eat, you are paying five mana to detonate your own creature for a board sweep. It wants a board already crowded with expendable bodies and an opponent who has overextended.