Karlov's Crossbow (UNK-CA06A) - Unknown Event

Whenever equipped creature attacks, sacrifice Karlov's Crossbow and destroy target creature an opponent controls.
Equip {1}
Forecast — {0}, Reveal Karlov's Crossbow from your hand: For the remainder of the game, spells you cast named Karlov's Crossbow cost {1} less to cast. (Activate only during your upkeep and only once each turn.)