Cheapest priced copy (Journey into Nyx): $2.99 at Card Kingdom, near mint, their price list as of .
Eidolon of the Great Revel 
Enchantment Creature — Spirit · 2/2 · Rare · Journey into Nyx · #94
Whenever a player casts a spell with mana value 3 or less, this creature deals 2 damage to that player.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $2.99 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Masters 25 | 128 | Rare | $3.99 | $5.99 |
| Journey into Nyx | 94 | Rare | $2.99 | $4.99 |
| The List | JOU-94 | Rare | $3.99 | — |
| Store Championships | 14 | Rare | — | $3.99 |
| Secret Lair Drop | 422 | Rare | $6.99 | $5.99 |
3 rulings from Wizards of the Coast
- 16 March 2018Casting Eidolon of the Great Revel doesn't cause its own ability to trigger. It must be on the battlefield when the spell is cast for its ability to trigger.
- 16 March 2018The amount of mana spent to cast a spell doesn't change its mana value. For example, a card cast with its morph ability has a mana value of 0 even though {3} was paid.
- 16 March 2018The mana value of a spell with {X} in its mana cost includes the value chosen for X.