Endos was formally the Dark Aeon's liaison. He appeared physically frail but firm and he spoke as if he had allied himself with the Dark Aeon in a bid for power.
In reality, it was the reverse; Endos was the one in possession of power and was offering that power to the Aeon for its second attempt to devour Nautilus in exchange for unknown benefits. Benefits that he would gain without getting his own hands dirty or alerting any of Nautilus' citizens of his involvement. They lingered within the Beyond, biding their time.
The arrival of Xenmas and Pyramid Head gave him the opportunity to distance himself even further from the impending attack on Nautilus. His hands would remain clean regardless of whatever they chose to do.
Endos tempted both Xemnas and Pyramid Head with what they truly desired. Xemnas sought control in a city that lorded over all with its own power. Pyramid Head sought punishment - a proof of his own existence and purpose. Both required power to obtain their desires and so they took Endos' offer.
Once the two made their agreements with Endos, the boy produced a vial containing radiant violet light: a remnant of Isis to be used as a tool for power. With Endos' instruction, Xemnas injected the vial's contents into the Aeon's crust. The power of the deceased Deva of Glass course through them, a small portion of it spilling into them as the Dark Aeon consumed the majority of Isis' essence.
Satisfied by the outcome, Endos knew the two Wakened were ready and vanished. Xemnas and Pyramid Head then start steering the rejuvenated Dark Aeon towards Nautilus.
A few years later, he suddenly returned and found Xemnas in a dying state due to having had Isis' essence in his body too long. He makes another deal to remove it from him and Xemnas accepted the offer. Endos was successful in removing it but then Xemnas attacked him, not having much longer to live. He kills him with two poisoned daggers before then forcing Xemnas' face into the mercury river in the Western District to finish him off.
Not much else is known about him nor is it clear if he's an ally or an enemy.
Description of character personality.
Important relationships and connections.