Aeturnus is one of the officers who served with Praepositus in the human army opposing the Daedra. After the defeat he, unlike Praepositus, managed to regroup with other survivors and to rebuild a community (see Aeturnus' army). He stayed with the army up to just before the cloning machine had been finished.
He had left to track down Praepositus for being a traitor, serving Uterio was too much of an insult to bare. He and a crack squad boarded onto the army's ship and set towards a forest which Praepositus had entered.
The troops continued on foot whilst the ship stayed landed nearby. Aeturnus gave the order for the forest to be burned ahead of their path, the forest being so thick. This disturbed Belldandy and the Dark Gnomes into combat. The humans advanced after a spree of heavy fire. Bayonet first, his troops marched through the burning forest.
The Dark Gnomes had cast on them some paralytic spells which, in the end, sent the soldiers into a full on rout. Aeturnus was forced to retreat and regroup.
Finding no extra troops to spare, Aeturnus set off alone to finish what he had started. He travelled in a one man ship and was soon able to catch up to Praepositus but instead of killing him, ended being hired as his mercenary to help him with his quest for the Keruvim.
Threatened by the escape of Blackout, Aeturnus flees back to his army and advances on the recovering foe. He takes with him 4 majors, a ship each, but is soon ambushed by Blackout's knights. The humans aboard his ship started a mutiny about this time, but Ravat's timely arrival saved him.
Currently, Aeturnus is a 'guest' of Nabonidus's in the hellish world of Bralgu.