Belzenlok, Cabal Overlord

Flying, Trample
{b}{b}{b}, discard a card: Search target opponent's library for a historic card and exile it, then that
player shuffles their library. For as long as that
card remains exiled, you may cast it without
paying its mana cost by paying X life, where X is
its converted mana cost. Activate this ability only
at any time you could cast a sorcery.