Stream of Thought is a common Sorcery card from Modern Horizons (MH1), collector number 71. Current market price: $0.19 (foil $1.96), TCGplayer market prices via Scryfall.
Target player mills four cards. You shuffle up to four cards from your graveyard into your library. Replicate {2}{U}{U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)