Engulfing Slagwurm

Combat math stops working the moment this thing touches it. Most deathtouch-on-a-stick designs let you trade up: a small body kills a big one, but the small body usually dies too. This one inverts the exchange entirely. A 7/7 already wins most ground fights on raw size, and the destroy-on-block clause means it does not even take the damage: anything that blocks it or that it blocks is gone before damage would resolve, so it eats the attacker or blocker without the trade. The defender still has one outlet, and it matters here: with no trample, a chump block stops the wurm cold, sacrificing a body to keep its controller's life total intact for a turn. What the chump cannot avoid is the lifegain rider. The bigger the creature your opponent throws in front of it, the more life you bank for killing that creature, so blocking with something fat (the natural instinct against a 7/7) only widens the gap. The cost is the obvious tax for breaking combat this cleanly. Seven mana for a creature that has to block or be blocked to do its work means it does nothing the turn it lands and nothing against a board that simply refuses to engage. It is removal that must be threatened rather than aimed, and that conditionality, not the rate, explains why a 7/7 with repeatable, lifegain-stapled destruction costs seven instead of four.