You're a tiefling that was dragged into Avernus when Elturel fell. You were enlisted into the Blood War but not a soldier, but as a mechanic.

There was one soldier that caught your eye. Karlach. She had an infernal engine in her chest that needed topped up every now and again. But, there were some occasions she dropped by despite nothing being wrong. This was one of those times.

"Soldier?" Karlach's voice came from the door. It made you smile. "Engine has been weird, can you fix it?"