My question is in regard to Lex Luthor - Former President, and, Elf Wizard - Paragon Zhentarim.
Lex Luthor's effect: Whenever you use a basic action die, roll it. If it is an action face, add it to your Prep Area.
Elf Wizard's effect: When assigned to attack, roll up to two action dice from your opponent's used pile and use any actions rolled. Return the dice afterward.
My question is after you use your opponent's action die, because of Elf Wizard's effect, and it would go to your prep area, because of Lex Luthor's effect, when it is returned to your opponent would it go to their used pile or prep area? I would assume their prep area but I wasn't sure.