Diary of Dreams is a uncommon Artifact — Book card from Secrets of Strixhaven (SOS), collector number 248. Current market price: $0.22 (foil $0.33), TCGplayer market prices via Scryfall.
Whenever you cast an instant or sorcery spell, put a page counter on this artifact. {5}, {T}: Draw a card. This ability costs {1} less to activate for each page counter on this artifact.