Diminisher Witch

Bargain gives blue a resource-conversion clause it rarely gets: a way to turn spent value into board disruption. The body arrives regardless, so the sacrifice never gates whether you get a creature; it gates whether that creature also drops a Cursed Role onto the strongest thing an opponent controls, shrinking it to a 1/1. That framing is what makes the card read as a tempo piece rather than a tax. You feed it something already cashed in (a Food token, a spare Treasure, a spent enchantment, a leftover creature token that has outlived its purpose) and get a downgrade stapled to an opposing threat, all off one spell. Note the overwrite rule cuts only one way: the Cursed Role replaces another Role you already control on that creature, not one the opponent installed, so this is not a way to strip an opponent's boon. It is a way to attach your own penalty. Blue has always struggled to interact profitably with large creatures without hard removal or a bounce spell that just resets the clock; here the interaction is folded into a body that keeps attacking. The 1/1 downgrade is not a kill, and against creatures already small the Role does little, which is the honest ceiling on the design. But as a means of laundering dead permanents into a permanent stat reduction on the opponent's best blocker, it captures Bargain's core idea cleanly: value you were finished with becomes pressure they now have to answer.