Aard is the first Sign Geralt 'learns' over the course of the game; one cannot finish the Prologue without it as it is necessary to break through a wall of debris to exit the witchers' laboratory. Its icon is based on the alchemical symbol for Air. It is the sign that the witcher uses the most. Outside of combat, Aard is most often used to clear a path, either by blowing down a wall or blowing apart a pile of debris. During combat it can stun, knockdown or disarm an opponent. The witcher's skill with the sign is developed through the allocation of talents.