Ascalon is the sword that Saint George used to kill a Dragon. It was previously kept by the Church along with the Durandal and the Excaliburs. In Volume 4, Issei received the sword from the leader of the Angels, the Archangel Michael, prior to the meeting of the Three Factions. Issei mainly uses the sword in situations where cutting a target is necessary, when countering sword-wielding opponents, or against Dragons and/or Dragon-related beings, storing it inside his Boosted Gear when not in use. He mostly lends it to Xenovia during fights in which Durandal is unavailable or unsuited to the situation. He once lent Ascalon to Yuuto Kiba.
In the later Volumes starting on Volume 14, instead of using the actual sword Issei started to transfer the dragon-slaying ability of Ascalon to his punches and attacks.
Ascalon has the appearance of a European sword with a reddish purple grip and a golden hilt with stylized crosses at the edges of the guard.
In the anime, the guard has a different appearance, and more resembles four golden dragon claws sticking upwards. The sword has the appearance of a European sword with a grey hilt, a red diamond design imprinted on it surrounded by four blue lines that curve slightly and a golden pommel in the shape of a cone-like arrow. The blade is also notched three times on both sides near the bottom and the fuller, which reaches slightly above the notches, has a gold edge in the shape of a large pearl and the rest is colored purple.
Ascalon has all of the powers common to a legendary Holy Sword, along with the ability to slay Dragons and Dragon-related beings. Issei has demonstrated the ability to attack from a distance with the sword by releasing its holy aura. When stored inside Issei's Boosted Gear, he can transfer power into it. Issei has also learned how to channel the Dragon Slayer power of Ascalon into his Balance Breaker punches, allowing him to harm Dragons far more easily. Later, Issei managed to combine Ascalon's Dragon Slayer ability with his Crimson Blaster. As of Volume 25, Issei can also endow Ascalon with Penetrate and Boost, with the effect staying even after he launches it as a projectile against Vidar.
- In episode 11 and 12 of the anime's second season, Issei showed the ability to extend the blade more than it's normal length, whether this is a normal ability of the sword or an ability gained with the fusion of the Boosted Gear is not clear.
- The word Ascalon comes from Ashkelon which means "to weigh."