Marchesa's Decree

Mana cost: {3}{B}
Type: Enchantment
Set: Treasure Chest #20 (uncommon)

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

Marchesa's Decree has 4 printings, first in Conspiracy: Take the Crown (2016). EDHREC ranks it #6,983 among Commander cards. It appears most in Queen Marchesa decks (6,848 on EDHREC). 1 public deck on TCG runs it. It has 4 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: not legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run Marchesa's Decree

Wretched Ranks - Foundations Commander, led by Ghoulcaller Gisa

Commanders that run Marchesa's Decree most

Deck counts from EDHREC.

Often played with Marchesa's Decree

Cards that show up in the same decks on EDHREC.

Rulings

2016-08-23: Abilities that trigger whenever you "become the monarch" trigger only if you aren't already the monarch. For example, if you are already the monarch as Custodi Lich enters the battlefield, its last ability won't trigger.
2016-08-23: Being the monarch carries two inherent triggered abilities. "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."
2016-08-23: 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.
2016-08-23: The game starts with no monarch. Once an effect makes one player the monarch, the game will have exactly one monarch from that point forward.