You can banish this card from your hand or field; add 1 "Aleister" monster from your Deck to your hand, then if this effect was activated on the field, immediately after this effect resolves, you can Normal Summon 1 Spellcaster monster. If a face-up Fusion Monster(s) you control is sent to the GY, except by battle, while this card is in your GY (except during the Damage Step): You can Special Summon this card, then you can Fusion Summon 1 "Invoked" monster from your Extra Deck, using monsters from your hand or field. You can only use each effect of "Aiwass, Divine Spirit of the Law" once per turn.
