Son of Kavreshar and Thea Vermillion, twin brother of Mercy Olivier. The twins were adopted as infants by Ysabeau Chanuier and Martan Olivier, who raised them as their own children. Justen was born with unnerving red eyes. he and his sister inherited a number of powers from their demonic father, including exceptional strength, various immunities, teleportation and limited shapeshifting, and the ability to generate an aura of intense heat.
A Legend Lore cast on him and his sister as children, by Alma, went as follows: Twinned vessels, separate but inseparable, where bloods are reunited and reborn, a father's wishes are inherited and dashed, and destiny is created, not bestowed.
Justen is seriously (but not exclusively) romantically involved with Xandhìl Órecalo.