In his early life, before becoming a god, Vivec was an advisor to Indoril Nerevar along with the other members of the Tribunal. Vivec is worshipped by the Dunmer as a symbol of 'mastery,' as well as 'duality' given his Chimer/Dunmer complexion, hermaphroditic appearance, and sinister nature hidden behind his benevolence due to his relations to Mephala.
3.6 Akaviri Invasion and the Ebonheart Pact.