Kashtira Unicorn [MP23-EN164] Prismatic Secret Rare

If you control no monsters, you can Special Summon this card (from your hand). You can only use each of the following effects of "Kashtira Unicorn" once per turn. During your Main Phase: You can add 1 "Kashtira" Spell from your Deck to your hand. When this card declares an attack, or if your opponent activates a monster effect (except during the Damage Step): You can look at your opponent's Extra Deck, and if you do, banish 1 monster from it, face-down.