Challenge in "The Sanctuary", Emilia (RZ/S116-E030) [Re:ZERO -Starting Life in Another World- Vol.3]

[AUTO] [Put 1 card from your hand into your waiting room] When this card is placed on the stage from your hand, you may pay the cost. If you do, choose 1 level X or lower "Magic" or "Weapon" character in your waiting room, and return it to your hand. X is equal to the number of "Let's Sing of the Future Together With You, Emilia" in your waiting room.