Cheapest priced copy (Zendikar Rising): $2.79 at Card Kingdom, near mint, their price list as of .
Archon of Emeria 
Creature — Archon · 2/3 · Rare · Zendikar Rising Promos · #4p
Flying
Each player can't cast more than one spell each turn.
Nonbasic lands your opponents control enter tapped.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $2.79 to $8.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mystery Booster 2 | 4 | Rare | $2.99 | — |
| Zendikar Rising Promos | 4p | Rare | $2.99 | $4.49 |
| Zendikar Rising Promos | 4s | Rare | — | $8.49 |
| Zendikar Rising | 4 | Rare | $2.79 | $3.49 |
| Zendikar Rising | 315 | Rare | $3.99 | $4.99 |
3 rulings from Wizards of the Coast
- 25 September 2020If an effect says that a land enters tapped unless a condition is met or a cost is paid, that land enters tapped even if that condition is met or that cost is paid if it's affected by Archon of Emeria's second ability.
- 25 September 2020If you cast a spell that was countered, you can't cast another spell during the same turn.
- 25 September 2020Archon of Emeria looks at the entire turn to see if a player has cast a spell, even if Archon of Emeria wasn't on the battlefield when that spell was cast. Notably, you can't cast Archon of Emeria and then cast another spell during the same turn.