Charred Foyer // Warped Space (Borderless)

Charred Foyer At the beginning of your card of your upkeep, exile the top card of your library. You may play it this turn / Warped Space Once each turn, you may pay 0 rather than pay the mana cost for a spell you cast from exile.

(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it)