Silverquill, the Disputant

Casualty grafted onto a static ability is the design turn here: instead of buying the copy with a sacrifice keyword printed on each spell, this hands every instant and sorcery in your deck a built-in casualty 1 the moment this dragon is on the battlefield. That reframes the whole cost structure of a spellslinger build. Casualty has always asked you to pay in bodies for a doubled effect, but it only ever lived on the handful of spells that shipped with the keyword. Wiring it to a permanent means the trade is now available on burn, removal, card draw, and tutors alike. The friction is real and self-limiting: each copy demands a creature with power 1 or greater, so the engine wants a stream of expendable one-power fodder rather than a single fat attacker. The 4/4 flying, vigilance body does double duty beyond enabling; it can pressure in the air and hold the ground on the same turn, so the sacrifice fodder that powers the copies goes to combat or the altar without leaving you exposed. The payoff is a spellslinger shell that spends its own small creatures as ammunition, then recoups them with the value each doubled spell generates.