Around 900,000 B.E., the alien Cleax hordes invaded Starmourn, and were stopped by an alliance of the Utan Mir, the Y'saari, the Quix, the Ta-deth, and the Vyar.
As was later discovered, it was during this invasion that they seeded Starmourn with genetic material that resulted in both the Oteel and the Nath-el.
The Vyar subsequently built the Sheol Locus to keep the Cleax out of Starmourn in the future.