When this card is activated: Add 1 "Regulus, the Prince of Endymion" or 1 monster that mentions it from your Deck to your hand, then if your opponent controls a monster, you can Special Summon 1 Spellcaster monster from your hand.

If a card(s) you control would be destroyed by battle or card effect, you can destroy 1 "Regulus, the Prince of Endymion" in your hand or face-up Monster Zone instead.