Echo of Eons is a mythic Sorcery card from Mystery Booster 2 (MB2), collector number 160. Current market price: $10.16 (foil $73.15), TCGplayer market prices via Scryfall.
Each player shuffles their hand and graveyard into their library, then draws seven cards. Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)