Custodi Lich — ruling 1

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.

Custodi Lich — ruling 2

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.

Custodi Lich — ruling 3

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.”

Custodi Lich — ruling 4

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.

Custodi Lich : règles, fonctionnement et interactions (MTG)

Custodi Lich is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When this creature enters, you become the monarch. Whenever you become the monarch, target player sacrifices a creature of their choice.

How it works : Custodi Lich

Original English text — Wizards of the Coast / Scryfall

#1August 23, 2016· Wizards of the Coast
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.
Card named in this ruling
The Monarch
#2August 23, 2016· Wizards of the Coast
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.
Card named in this ruling
The Monarch
#3August 23, 2016· Wizards of the Coast
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.”
Card named in this ruling
The Monarch
#4August 23, 2016· Wizards of the Coast
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.
Card named in this ruling
The Monarch