Whenever a player casts a spell with converted mana cost 3 or less, Eidolon of the Great Revel deals 2 damage to that player.
3/16/2018 Casting 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.
3/16/2018 The amount of mana spent to cast a spell doesn’t change its converted mana cost. For example, a card cast with its morph ability has a converted mana cost of 0 even though was paid.
3/16/2018 The converted mana cost of a spell with in its mana cost includes the value chosen for X.