From: Kir__Kanos | #003 Um....how'd they manage that?
The An-Xileel and the Hist basically united them against three common enemies(the oblivion gates, the empire, and the dunmer)
they ended the oblivion invasion in their province due to their numbers since they invaded Dagons realm itself. Drove the empire out of black marsh and then invaded Morrowind and the drove the dark elves out.
if you have any other questions about post-elder scrolls IV just ask me since im still reading it and finding out a lot of what happened after oblivion.
Red Mountain went off The Ministry of Truth in Vivec City(originally a moon from oblivion) lost its suspension in the air since Vivecs powers that were holding it up dissipated slamming into Vivec city and annihilating Vvardenfell.