Vul'tar Ravenblood is a Tiefling Arcane Trickster. His unnerving demonic appearance (i.e., red glowing eyes and the stench of brimstone that follows him) has not made him many allies during his travels.
Vul'tar was introduced to the party through Worren as a guide through the jungles of Xen'drik. It was at first believed that Vul'tar took the job as repayment for a debt he owed Worren but later revealed that, in fact, Worren was the one repaying the debt to Vul'tar. Vul'tar has given no reason as of yet on why he has really joined the group.
It was also revealed that at one time Vul'tar traveled with Maldazaar, including during the Summer of Fires. It is not yet known why or how the two parted ways.