Antikus, Cryptic Zenith

When Antikus, Cryptic Zenith enters the battlefield, search your library for an instant or sorcery card and exile it with a rune counter
on it.
Whenever Antikus deals combat damage to an opponent, you may pay {w}. If you do, you may cast a copy of a card you own in exile with a rune counter on it without paying its mana cost.