Trewin was a male Human who originated from the Undercity on the planet Taris. He functioned as the guardian of the gate separating the Outcast village from the zones overrun with rakghoul creatures.
When Hendar came back to the outcast village while being chased by rakghouls, he requested that Trewin unlock the gate to let him in. Despite not wanting Hendar to perish, Trewin denied him access, as he was convinced that this would enable the pursuing rakghouls to breach the village and eventually contaminate the remaining outcasts. Subsequently, Revan offered to fend off the rakghouls, ensuring Hendar's safe return. Trewin confessed to Revan that he was struck by the surface dweller's kindness and empathy, and felt he had gained valuable insight. Similar to the other Outcasts, he abandoned the village for the Promised Land once its location was found, leaving the gate unsecured as they departed the village.
Conversely, Revan had the option to decline assisting Hendar and observe his demise at the hands of the rakghouls, much to Hester's disappointment. Following this, Trewin would express his sorrow over Hendar's passing, while stating that he had cautioned him.
The facial representation of Trewin's character on the console varies from the PC/Nintendo Switch version. In the initial console release, his facial features are identical to those of Rukil.