Soul Swallower
Delirium asks a deck to do something most graveyard mechanics do not: stock four distinct card types rather than a raw count of cards, and this Wurm is the payoff that makes the threshold feel like a reward instead of a tax. The 3/3 trample body is deliberately undersized for four mana, a stat line that reads as a downpayment; meet the delirium condition and the upkeep trigger swells it to a 6/6 the following turn, then a 9/9, then bigger, with trample carrying the surplus through chump blocks. The wrinkle is the timing. The counters land only once per turn cycle, so the creature has to survive a full loop before it pays off, which leaves a removal spell one clean window to answer it while it is still a small body that has yet to grow. That delay is the cost the design charges for an effect that otherwise compounds without a ceiling: the card poses no immediate threat when it resolves, so the opponent gets a single cheap chance to kill it. It rewards the kind of self-mill and fetch-and-discard shell that naturally diversifies a graveyard (an instant, a sorcery, a creature, a land in the bin) and punishes the deck that splashes it without the supporting card-type spread. Left alone for two upkeeps, it stops being a fair creature and becomes a clock that ends games on its own.
