If you have an "Aleister" monster in your field, GY, or banishment: Activate 1 of these effects;
• Fusion Summon 1 "Invoked" Fusion Monster from your Extra Deck, by banishing 1 monster in your hand or field and 1 monster in your Deck as material.
• Fusion Summon 1 "Invoked" Fusion Monster from your Extra Deck, by banishing 1 monster you control and 1 face-up monster your opponent controls as material.
You can only activate 1 "Invocation - "Grail"" per turn.