Cheapest priced copy (Commander Legends): $1.29 at Card Kingdom, near mint, their price list as of .
Archon of Coronation 
Creature — Archon · 5/5 · Mythic · New Capenna Commander · #192
Flying
When this creature enters, you become the monarch.
As long as you're the monarch, damage doesn't cause you to lose life. (When a creature deals combat damage to you, its controller still becomes the monarch.)
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
3 printings · $1.29 to $9.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Legends | 9 | Mythic | $1.29 | $2.49 |
| Commander Legends | 616 | Mythic | $3.49 | $9.99 |
| New Capenna Commander | 192 | Mythic | $1.29 | — |
7 rulings from Wizards of the Coast
- 10 November 2020If 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.
- 10 November 2020If 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.
- 10 November 2020There 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."
- 10 November 2020The game starts with no monarch. Once an effect makes one player the monarch, the game will have exactly one monarch from that point forward. As a player becomes the monarch, the current monarch (if any) ceases being the monarch.
- 10 November 2020If 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.
- 10 November 2020While Archon of Coronation's last ability applies, damage dealt to you still has all effects other than causing you to lose life. For example, abilities that trigger on that damage being dealt still trigger; if the source has lifelink, its controller still gains life; and so on.
- 10 November 2020Combat damage dealt to you by a commander is still tracked, even if it didn't cause you to lose life.