Echo of Eons is a mythic Sorcery card from Modern Horizons (MH1), collector number 46. Current market price: $10.92 (foil $57.10), 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.)