Aaron was the Captain of the Janissaries and one of the few King Class swordsmen. He was absolute loyal to King Colora Valderish even after being evicted by him (by Pirrot Mask, who had taken the appearance of the king).
He was a swordsman that could use aura and it is said, that his powers would match that of Raphaello.
Though not a part of the final six, Aaron was a great hero who had played a key role within the core of the Shadow Labyrinth expedition. Aaron was a figure who had led hundreds of people out of the Shadow World to safety and had been a part of several joint operations with Desir, who he had been good friends with. He eventually died a glorious death.