Ranshi, the Chaos Smith

Haste
Whenever a player casts a spell with converted
mana cost 5 or greater, you may pay {r}. If you
do, that player exiles the top card of their
library. If it's a nonland card, you may cast it
without paying its mana cost.
{t}, Sacrifice a land: Copy target instant or
sorcery spell you control but don't own.