Daedra

The Daedra were the original inhabitants of the Infernal Planes of Oblivion.

Before the War
The Daedra were the sole inhabitants of the planes of Oblivion until a small army of barbarian humans from normal space fell through a hole in the fabric of reality and arrived in the planes. The Daedra considered these humans to be invaders and attacked them, but neither race was able to wholly eradicate the other, especially because the humans' forces were continuously added to by other human tribes that fell into Oblivion. The Daedra and the humans were forced to coexist by staying clear of the other's territories, but neither race forgot their hatred of the other and continued to skirmish throughout the ages.

The Oblivion Crisis
In 150,080 CMT, one Daedra was surprised by the sudden appearance of Yon and Praepediti in Oblivion. The Daedra proceeded to threaten them both, so Praepediti punched it into Yon, who punched it back into Praepediti, who decapitated it with a powerful kick to the head.

Meanwhile, the conflicts between the Daedra and the humans in Oblivion had escalated into an all-out war. One such battle involved a confrontation between an army of Daedra and an army of humans, who each stood on the other side of a river of lava. The Daedra cursed the humans and threw spears at them, killing six, but the rest protected themselves with shields and picked up the spears to throw them back. The Daedra's numbers were halved because their shields were too small to adequately protect themselves, so the Daedric commander sent in the Daedroth, crocodile-headed Daedra that leaped over the river and slashed at the humans with their claws. The Daedroth attacked the human army with such savagery that most of the humans fled in terror save for Praepositus and his shield-bearer, who swapped their uniforms with those of dead infantrymen and crawled to safety.

The Daedra were then attacked by Praepediti, who used the Wheeler to wipe out their entire battalion save for the commander. The Daedric commander challenged Prapediti to a no-weapons duel; Praepediti accepted, but cheated by using his foot blades to slice the commander in half. Praepediti then used the Wheeler to drive towards a black tower in the middle of an island, which was also Daedra territory. There, the elite Daedra Mehrunes Dagon led a legion of Daedra into battle against Praepediti. Vrentus noticed the battle between Praepediti and the Daedra and flew over to confront Mehrunes Dagon, expanding his form to a size that rivalled Dagon's own. Vrentus then threw a punch at Dagon that was so powerful that it created a spatial tear and threw the Daedric leader back, causing him to lose his grip on his trident, which then landed prongs-first in his own chest.

As Dagon lay dead or dying, the spatial tear expanded and Oblivion began to collapse as Vrentus had planned. Praepositus, Praepediti, Rahksha, and many of the human forces escaped through the tear back to normal space, and Vrentus teleported himself and Xigneo to the Forest of Lights, but the Daedra were presumably crushed in the event horizon of the collapsing reality and were scattered into atoms as a result, ceasing to exist as a species.

Legacy
The Observers watched and recorded the war between the Daedra and the humans from their station in Chronospace. September revealed this fact to Praepositus in 150,084 CMT.