Throne Warden — ruling 1

The last ability of Throne Warden checks to see if you're the monarch as your end step begins. If you're not, the ability won't trigger at all. You won't be able to do anything that would make you the monarch during your end step in time to have that ability trigger. The ability will also check to see if you're the monarch as it tries to resolve. If you're not the monarch at that time, the ability will have no effect.

Throne Warden — 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.

Throne Warden — 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."

Throne Warden — 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.

Throne Warden — ruling 5

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.

Throne Warden : règles, fonctionnement et interactions (MTG)

Throne Warden 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

At the beginning of your end step, if you're the monarch, put a +1/+1 counter on this creature.

How it works : Throne Warden

Original English text — Wizards of the Coast / Scryfall

#1August 23, 2016· Wizards of the Coast
The last ability of Throne Warden checks to see if you're the monarch as your end step begins. If you're not, the ability won't trigger at all. You won't be able to do anything that would make you the monarch during your end step in time to have that ability trigger. The ability will also check to see if you're the monarch as it tries to resolve. If you're not the monarch at that time, the ability will have no effect.
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
#5August 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