Court of Locthwain

When this enchantment enters, you become
the monarch.

At the beginning of your upkeep, exile the top card
of target opponent's library. You may play that card for as long as it remains exiled, and mana of any
type can be spent to cast it. If you're the monarch, until end of turn, you may cast a spell from among cards exiled with this enchantment without paying its mana cost.