عالم يكتنفه الظلام

(This card is always treated as a "Ninjitsu Art" card.)
When your "Ninja" monster inflicts battle damage to your opponent: You can target 1 card they control; destroy it. If this face-up card in its owner's Field Zone leaves the field by an opponent's card effect, and is sent to your GY or banished: You can target any number of "Ninja" monsters with different names in your GY; Special Summon them in face-down Defense Position.