Memory Deluge is a rare Instant card from Innistrad: Midnight Hunt Promos (PMID), collector number 62p. Current market price: $0.57 (foil $0.50), TCGplayer market prices via Scryfall.
Look at the top X cards of your library, where X is the amount of mana spent to cast this spell. Put two of them into your hand and the rest on the bottom of your library in a random order. Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)