Seymour Flux

The upkeep-payment engine is one of black's oldest bargains: pay a resource, draw a card, and here the price is life rather than mana. What sharpens it is the compounding body. Each life paid both fills your hand and puts a counter on the 5/5, so a stalled game becomes a self-funding snowball in which the same trigger digs deeper into your deck and steadily outsizes anything you traded off to get here. The design tension sits in the word "may." The payment is optional every upkeep, which means the card never drags you into a life spiral you cannot afford; it also means the growth only happens as fast as your life total tolerates. Under pressure the ability quietly switches off; in a grind it never stops. That puts the card in black's long line of advantage-for-attrition engines (the Phyrexian Arena tradition of buying cards with life), but it folds the card advantage and the win condition into a single permanent rather than splitting them across a draw engine and a separate finisher. The result punishes durdling and removal alike: answer it early and you have merely traded for a five-mana body, ignore it and it costs its controller only life to grow larger every turn while the same trigger refills the hand.