The Blind Raven
While at a bar in Ramshire, Siobhan talks with a group of three knights that describe working at an excavation site called The Maw. When the group later finds themselves at the site, they run into one of the three men, Tristen.
Tristen seems unaware that there is any real danger down in The Maw and believes that the stories of disappearances are all just rumors from the protesters in Camren. He has never gone down below surface level at the excavation though, as he works as a top-level guard, protecting the entrance-way from protesters and Kobold attacks.
After the events at The Maw and the ensuing Temporal Waves, they run into Tristen days later in The Temple of the Lost. He is killed during a confrontation with Sandar Meloris, in which Tristen is crazed and appears as an almost entirely different person. He had been, in the new timeline, surviving within the temple for over eight months, and was apparently sent in to discover the source of the power emanating from the temple, but was presumed dead after the mission had only one surviving member return.
Later on in the temple, the group finds a picture of Tristen from eight months prior, in what they assume is a room made specifically to taunt them for trying to shut the temple down. They realize that the pictures within that room as people who have been lost in the temple and possibly have some connection to them or to Sandar.