Quote Originally Posted by Absimiliard View Post
The Ascians actually wanted it to hover on the brink. A full blown flood of light consuming the entire world would've had similar results to their first (failed) attempt at initiating a rejoining. The only real difference is that it would be a void of light instead of darkness. Ardbert and his companions not doing what the Ascians anticipated is what actually tipped the scales beyond the breaking point and triggered the flood. The flood is what forced them to step up their timetables on the Source; to trigger a rejoining before the First could be completely consumed by the light.
Emet-Selch clearly state he created Vauthry following the failure of their plans involving Ardbert. (Innocence defeat cutscene)

From what I understand, the Emet-Selch got his 2nd idea for rejoining the First during the black rose factory cutscene (where he tells Varis they might not meet again in this lifetime; where he left for the first).