Wizard's Spellbook (Adventures in the Forgotten Realms)

Artifact Ñ Book - {T}: Exile target instant or sorcery card from a graveyard. Roll a d20. Activate only as a sorcery.
1Ñ9 | Copy that card. You may cast the copy.
10Ñ19 | Copy that card. You may cast the copy by paying {1} rather than paying its mana cost.
20 | Copy each card exiled with this artifact. You may cast any number of the copies without paying their mana costs.