Sidisi, Bane of Tarkir

When you cast Sidisi, Bane of Tarkir, you may exile a spell or permanent you control. If you do, search your library for a nonland card, cast it without paying its mana cost, then shuffle your library.
As long as Sidisi, Bane of Tarkir is on the stack, if another spell or ability would resolve, instead move it to the bottom of the stack.