Can you sacrifice a permanent in response to a spell that targets it?

When a player casts a spell or activates an ability that targets one of your permanents, that spell or ability goes on the stack. Before it resolves, both players receive priority and may respond. You can use this window to activate a sacrifice outlet — an ability that lets you sacrifice the targeted permanent as a cost — removing it from the battlefield entirely.

Once the targeted permanent leaves the battlefield, it is no longer a legal target. When the spell or ability tries to resolve, the game checks whether all targets are still legal (CR 608.2b). If every target is now illegal, the spell or ability is countered by the rules and does not resolve. This is commonly called "fizzling."

It is important to note that sacrificing is different from destroying: sacrifice cannot be prevented by indestructible, and the permanent never touches the graveyard via the spell — it was already moved there by the sacrifice. The key rule for priority and responding is CR 117.1, and the rule about illegal targets on resolution is CR 608.2b.

Concrete example: Your opponent casts Murder targeting your Grizzly Bears. In response, you activate Viscera Seer, sacrificing Grizzly Bears as the cost. When Murder tries to resolve, its target no longer exists on the battlefield, so it is countered by the rules and goes to the graveyard without effect.

Note: if the spell has multiple targets and at least one is still legal, the spell resolves and affects the remaining legal targets normally (CR 608.2b). Only a spell whose every target is illegal will fizzle completely.