Cheapest priced copy (Commander Masters): $0.99 at Card Kingdom, near mint, their price list as of .
Scourge of the Throne 
Creature — Dragon · 5/5 · Mythic · Foundations Commander · #173
Flying
Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)
Whenever this creature attacks for the first time each turn, if it's attacking the player with the most life or tied for most life, untap all attacking creatures. After this phase, there is an additional combat phase.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
9 printings · $0.99 to $32.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Masters | 253 | Rare | $0.99 | $2.99 |
| Commander Masters | 549 | Rare | — | — |
| Conspiracy | 35 | Mythic | $1.29 | $16.99 |
| Foundations Commander | 173 | Mythic | $0.99 | — |
| Tales of Middle-earth Commander | 225 | Mythic | $0.99 | — |
| Murders at Karlov Manor Commander | 160 | Rare | $0.99 | — |
| The List | CNS-35 | Mythic | $1.29 | $1.79 |
| Secret Lair Drop (Stardrake) | 1033 | Mythic | $27.99 | $32.99 |
| Tarkir: Dragonstorm Commander | 230 | Rare | $0.99 | — |
5 rulings from Wizards of the Coast
- 29 May 2014The +1/+1 counter is put on the creature before blockers are declared.
- 29 May 2014Once dethrone triggers, it doesn't matter what happens to the players' life totals before the ability resolves. You'll put a +1/+1 counter on the creature even if the defending player doesn't have the most life as the ability resolves.
- 29 May 2014Scourge of the Throne's ability has an intervening "if" clause. It must be attacking the player with the most life or tied with the most life both when it's declared as an attacker and as it starts to resolve for it to have any effect. If, at either time, the player isn't the one with the most life or tied for the most life, the ability will have no effect. Notably, this is different than how dethrone works. (Dethrone checks only once to see if the ability triggers.)
- 29 May 2014In a Two-Headed Giant game, dethrone will trigger if the creature attacks either player on the team with the most life or tied for the most life.
- 28 July 2023Dethrone doesn't trigger if the creature attacks a planeswalker, even if its controller has the most life. The same is true if the creature attacks a battle, even if its protector has the most life.