Xaeyruudh

Though he normally sticks with the form of a blue tiefling, Xaeyruudh is a doppelganger serving on the Venture II out of gratitude for his rescue. He and other doppelgangers were under the control of the hag Nightwhisper during her plot to abduct and cook up orphan children. Xaeyruudh was taken prisoner in a fight that saw the other doppelgangers killed and the party discovered the hag had branded him, forcibly controlling him with her dark magic. Charles "Chuck" Ling managed to remove the curse mark and keep Xaeyruudh alive through the process.
When the party returned with the rescued children, Xaeyruudh was dismayed to learn that Ürek had been killed and Chuck chose to stay behind to hunt Nightwhisper. He owed Chuck his life and would not let that debt go unpaid. Bakris extended an offer for Xaeyruudh to join the Venture II's crew and the doppelganger accepted, gaining the Venture Boys another ally.
In battle, Xaeyruudh makes the most of his shapechanging abilities. He will transform from an average-sized humanoid into a smaller one to dodge blows, though much to his chagrin his clothes do not shrink with him. His enthrallment by Nightwhisper also left him fey-touched, giving him a unique ability not possessed by other doppelgangers. Whereas the average doppelganger can only copy appearances, Xaeyruudh can use the innate abilities of whoever he's copying such as innate magics or a dragonborn's breath weapon. While Xaeyruudh is not a natural or very experienced fighter, these abilities make him capable of holding his own as he surprises opponents with ever-changing tactics.