Heartless Summoning

Knocking off every creature spell is the kind of acceleration that breaks games open, so the -1/-1 to your whole board is the toll for it. The discount slices generic mana off any cost, so a drop comes free and a drop pays just ; the static debuff is what stops that from being a clean upgrade, since a 1/1 cast for nothing arrives as a dead 0/0 and a 2/2 limps in at 1/1. The penalty stays survivable only if your bodies are big enough to eat it, which steers the card away from the goodstuff piles cost-reducers usually want and toward two distinct homes: a ramp shell that dumps fatties out early and shrugs off the static debuff, and a combo shell that wants enters-the-battlefield creatures it can flicker or loop while the -1/-1 turns them into self-destructing fodder, grinding their mana value down toward nothing. The interaction with cheap creatures is the sharpest edge: a 1/1 the discount pushes to free still resolves, then dies to the toughness reduction, which combo builders read as a feature rather than a flaw. Most black cost-reduction smooths out a curve. This one demands you answer the downside before you ever name the upside.