Aegir is a Secondary Pallasite armed with a gauntlet called the Phantom Arm, leading the assault on Palaestra under Hyperion’s orders.
He is the one who challenges Libra Genbu to battle, branding Hyperion’s sword. After killing Genbu and losing the sword because Genbu took off a little chip from the sword, he is quickly defeated and seemingly killed by an avenging Koga when he decides to kill the young Pegasus.
He later returns, still alive but with an almost destroyed Chronotector. Attacking the Steel Saints, he resurrects his Chronotector and Phantom Arm into a new, more powerful form and easily dominates the Steel Saints. But in the end, he is be defeated at the hands, or rather feet, of Unicorn Jabu.