You can send 1 Spellcaster monster, or 1 Spell/Trap that mentions "Dark Magician", from your hand or face-up field to the GY; Special Summon this card from your hand. During your Main Phase: You can Fusion Summon 1 Fusion Monster from your Extra Deck, using monsters from your hand or field as material, including a Spellcaster monster. You can only use each effect of "Timaeus the United Dragon" once per turn.