Ascalon

Ascalon is one of the four Holy Swords known as the Dragon Slayer Sword. It is a sword previously used by Saint George to kill a Dragon.

Summary
Ascalon is the sword that Saint George used to kill a Dragon. In volume 4, Issei receives the sword from the leader of the Angels, the Archangel Michael, prior to the meeting of the three factions. Issei rarely uses the sword, having it stored inside his Boosted Gear, and mostly lends it to Xenovia during fights.

Abilities
Ascalon has the ability to slay Dragons and Dragon-related beings. When stored inside Issei's Boosted Gear, he can transfer power to it.