Trewin was a Human male native to the Undercity of Taris. He was the gatekeeper who attended the gate between the Outcast village and the rakghoul-infested lands.
When Hendar returned to the outcast village pursued by rakghouls, he asked Trewin to open the gate so he could get in. Although unwilling to leave Hendar to die, Trewin refused him entry, believing that this would allow the pursuing rakghoul to enter the village and ultimately infect the other outcasts. Revan then volunteered to fight off the rakghoul so that Hendar could return safely. Trewin admitted to Revan that he was impressed by the up-worlder's generosity and compassion, and believed he had learned a lesson from it. He like the other Outcasts left the village for the Promised Land when its location was discovered and left the gate open at the village's departure.
Alternatively, Revan could have refused to help Hendar and watched him get killed by the rakghoul, to Hester's dismay. Trewin would then voice his regret over Hendar's death, but said he warned him. Trewin was voiced by Cam Clarke.
Trewin's console character model has a different facial model than his PC/Nintendo Switch counterpart. In the original console version, he shares a facial model with Rukil.