Declare 1 Monster Card name. If the declared card is in your opponent's Deck, add 1 of that card to your opponent's hand.
Rulings
Individual Card FAQs
If you activate "Dark Designator" and your opponent says he/she has no cards in their Deck of that name, you may check the Deck to verify.
You cannot declare a nonexistent card for "Dark Designator".
Your opponent must show you the card added to his hand.
Netrep Rulings
If the player required to search for the Monster Card designated by "Dark Designator's" effect does not have the specified card in his/her Deck, the controller of "Dark Designator" may search the opponent's Deck to verify this.
Spell|
Normal