Zaffai and the Tempests
Free spells have always been the most dangerous well in the game, and the usual guardrail is the one-shot: an alternative cost, a payment, a card exiled after. This one hands you the effect on a recurring clock instead. Once during each of your turns, one instant or sorcery leaves your hand at no cost, and the balancing act lives entirely in the pacing. You cannot storm off with it; the free cast is capped at one per turn, so the reward scales with how much a single big spell can generate rather than how many small ones you can chain. That reframes the whole cost curve. Your hand stops being a sequence of things you can afford this turn and becomes a menu where the most expensive spell is often the cheapest to resolve, which pushes the build toward top-heavy bombs rather than cheap cantrips. The 5/7 body matters more than free-spell payoffs usually manage: at seven mana this is not a fragile engine you protect behind a wall but a genuine blocker that can eat an attack and still enable the free cast on your turn. Recurring free-cast effects tend toward the same failure poles, doing nothing or doing everything; gating the ability to one spell a turn keeps the ceiling in view while leaving the floor high, because even one free bomb per turn compounds fast.
