Volcano Hellion

Echo is usually a one-time mana tax, a fixed number you pay at your next upkeep to keep a permanent you got at a discount. Here the keyword is pegged to your life total, which warps it into something far stranger: the body entered by burning you, and the following upkeep asks for generic mana equal to whatever life you have left, or you hand it back. The enters trigger is the engine. You choose the amount, it can't be prevented, and the full chosen number lands on both you and a target creature at once, so the card doubles as a removal spell that scales to whatever you're willing to eat and a 6/5 that arrives already bleeding. Most one-shot burn caps at a fixed figure; this points an arbitrary amount at a single creature, paid for in your own life rather than mana. That's the closed loop the design turns on: the harder you swing the entry to kill something big, the lower your life total, and the cheaper echo becomes the next turn, since echo reads your current life rather than a set number. The two halves answer each other. The entry drains life to do its work, and echo's mana cost shrinks in lockstep with the damage you've already absorbed. A Hellion oversized for four mana precisely because the rest of the card keeps charging you to keep it around.