Keeper of Dragon Magic

If this card is Normal or Special Summoned: You can discard 1 card; add 1 "Polymerization" Normal Spell or "Fusion" Normal Spell from your Deck to your hand. You can reveal 1 Fusion Monster in your Extra Deck; Special Summon 1 of the Fusion Materials mentioned on that monster from your GY, in face-down Defense Position. You can only use each effect of "Keeper of Dragon Magic" once per turn. You cannot Special Summon from the Extra Deck, except Fusion Monsters, the turn you activate either of this card's effects.