IF

Play in current battle when opponent concedes. Player may discard any number of cards left in hand to top of Draw Pile. In the next battle, normal rules for duplication will still apply. This card cannot be played in reaction to the owning player conceding. This card may not be avoided or negated since it is a defensive card play.

Exceptions/Errata
Orion's Boom Tube is played offensively on your turn as you concede.

Meta Rules
Meta #69 Specials which affect what happens after an opponent has conceded the battle cannot be played in response to a player conceding before the battle begins (an option both players have).

Meta #126 When an opponent concedes, only one Special may be played in response to that concession - even if multiple cards are playable after an opponent concedes.