Agents of Ioun
The tiefling Dorian Kahlir revealed himself as Vesta’s father during a battle in Harken Keep. He was apparently sent by Dispiria Kahlir to assist the Circle of Iron with the invasion of Harkenwold. Vesta didn’t learn much during their first encounter, aside from the fact that Dorian brought her to the Temple of Ioun so that she would be safe after her mother’s death, but before he was turned into a vampire. Dorian escaped the encounter by dissolving into a mist and floating away (presumably a vampire ability).