Normally, when a "Perfect Guard" unit is placed on (GC) from anywhere, by discarding a card of the same clan from hand as cost, the player may choose one of their units of the same clan that is being attacked, and that chosen unit cannot be hit by the attack until end of the battle, no matter how much power the attack has, and no damage check must be performed as a result. Starting from Booster Set 16: Legion of Dragons & Blades, you no longer are required to discard a card nor choose a unit of the same clan due to Clan Fight regulations making those restrictions redundant in card texts.