Vance was formerly a Warlock. During his time as a Guardian, he apparently knew Eris Morn. At one point, he suffered a near-death experience which also blinded him.
After Mara Sov opened the Reef to the Guardians, the disciples of Osiris concluded that the Tower would never be ready for the Trials despite Lord Shaxx's efforts training Guardians in the Crucible. They took the Awoken opening the Reef as an opportunity to train Guardians in the Trials. Sister Faora sent Vance to the Vestian Outpost to inform the incoming Guardians of the Trials and give passage to those Guardians who were brave enough to enter.