Tooth Collector

Delirium usually rewards you with a bigger body or a cheaper spell; here it turns on a repeatable soft-removal drip instead. The enters-the-battlefield -1/-1 is the down payment, enough to kill an X/1 or shave a blocker on the turn it lands. The delirium clause is where the design gets pointed: fill your graveyard with four card types and every opposing upkeep starts with another -1/-1, aimed at whatever that player controls. That is a grind engine dressed as an aggressive three-drop, and the split matters. The enters half is proactive and immediate; the delirium half is passive, recurring, and works on the opponent's clock rather than yours, so it keeps taxing their board so long as it survives to keep the trigger online. The -1/-1 shrinking, rather than a straight kill spell, is the constraint doing the work: it clears small utility creatures and mana dorks reliably but bounces off anything with real toughness, keeping the recurring effect a nuisance rather than a lock. The whole card is a study in how black delirium payoffs can be built around attrition instead of tempo, asking you to seed the graveyard early and then let a modest body do slow, cumulative damage to the other side's creature count.