Ashtrashen - Gate to the Worlds Beyond

You can target any number of face-down cards you control; add "Ashtra" cards from your Deck to your hand with different names from each other, except Field Spells, equal to the number of those targeted cards that are still face-down, then send those face-down cards to the GY. If a card(s) becomes Set on the field, while you control an "Ashtra" monster and a face-down card: You can target 1 card on the field; return it to the hand. You can only use each effect of "Ashtrashen - Gate to the Worlds Beyond" once per turn.