Apotheosis is a dark fantasy, story-rich, open world expansion for The Elder Scrolls V: Skyrim set across the 17 Planes of Oblivion, and 'Dreamsleeve', in an echo of a fallen world.
"Hail to the ancient spirits
Teachers, testers, weal and woe
Hard lessons, but needful too
For this world is full of foes
Hail Molag Bal, the Prince of Pain
Brutal master, lord of troubles
Giver of strength to slay and strive
For men are meant to struggle"
Transcription of "Hail to the Ancient Spirits"
En.m.uesp.net
Will Molag Bal make any references to the Vestige or the Dark Anchors?
References like these really depend on the context.
But we will be taking the events and lore additions of ESO as part of the general canon.