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.

Wilds of Eldraine Commander

When Court of Locthwain enters the battlefield, 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 Court of Locthwain without paying its mana cost.

If combat damage dealt to the monarch causes that player to lose the game, the triggered ability that causes the controller of the attacking creature to become the monarch doesn't resolve. In most cases, the controller of the attacking creature will still become the monarch as it is likely their turn.

If the monarch leaves the game during another player's turn, that player becomes the monarch. If the monarch leaves the game during their turn, the next player in turn order becomes the monarch.

If the triggered ability that causes the monarch to draw a card goes on the stack and a different player becomes the monarch before that ability resolves, the first player will still draw the card.

The game starts with no monarch. As a player becomes the monarch, the current monarch (if any) ceases being the monarch. There is never more than one monarch at a time.

The six types of mana are white, blue, black, red, green, and colorless. Snow mana is not a type of mana. Court of Locthwain won't let you pay a snow cost using mana produced by a nonsnow source.

There are two inherent triggered abilities associated with being the monarch. These triggered abilities have no source and are controlled by the player who was the monarch at the time the abilities triggered. The full texts of these abilities are "At the beginning of the monarch's end step, that player draws a card" and "Whenever a creature deals combat damage to the monarch, its controller becomes the monarch."

You may play the exiled cards (and spend mana of any type to do so) even if Court of Locthwain leaves the battlefield. If another player gains control of Court of Locthwain, that player can't play the cards, and you still can.

You pay the costs for an exiled card if you cast it. You may pay any alternative costs the card has rather than the card's mana cost.