Rincewind, Failed Wizard can't be sacrificed.

When you cast this spell, search your library for an instant or sorcery card and exile it with three time counters on it. If it doesn’t have suspend, it gains suspend. Then shuffle.

As long as you own a suspended card, whenever you cast a spell, flip a coin. If you lose the flip, counter that spell.

Whenever Rincewind, Failed Wizard becomes the target of a spell or ability, exile him. Return him to the battlefield under his owner’s control at the beginning of the next end step.