Marchesa's Decree

When Marchesa's Decree enters, you become the monarch.
Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life.

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.

Court of Ambition

When Court of Ambition enters, you become the monarch.
At the beginning of your upkeep, each opponent loses 3 life unless they discard a card. If you're the monarch, instead each opponent loses 6 life unless they discard two cards.

Garrulous Sycophant

At the beginning of your end step, if you're the monarch, each opponent loses 1 life and you gain 1 life.

Starscream, Seeker Leader

Living metal (During your turn, this Vehicle is also a creature.)
Flying, menace, haste
Whenever Starscream deals combat damage to a player, if there is no monarch, that player becomes the monarch.
Whenever you become the monarch, convert Starscream.

Starscream, Power Hungry

More Than Meets the Eye {2}{B} (You may cast this card converted for {2}{B}.)
Flying
Whenever you draw a card, if you're the monarch, target opponent loses 2 life.
Whenever one or more creatures deal combat damage to you, convert Starscream.

Starscream, Power Hungry // Starscream, Seeker Leader

Sheoldred, the Apocalypse

Deathtouch
Whenever you draw a card, you gain 2 life.
Whenever an opponent draws a card, they lose 2 life.