Thulgrim spent forty years in the lightless fighting pits of the Underdark, not as a champion, but as a survivor who learned the exact PSI required to snap a femur and the precise angle to collapse a lung. He didn't find religion through a vision of grace, but through a cold, mathematical epiphany: the 'Grand Machine' of the world was grinding to a halt because its biological components—people—were too fragile and poorly maintained. He saw a master stone-carver die of a simple festering wound and felt a rage not of grief, but of industrial offense. It was a waste of a high-value asset.
He pledged himself to the tenets of Life magic, reinterpreting holy scriptures as a maintenance manual. To Thulgrim, the pulse is a rhythmic piston, and blood is merely hydraulic fluid. He escaped the pits by 'repairing' his fellow slaves just enough to stage a high-efficiency revolt, leaving behind a trail of survivors who felt less like saved souls and more like patched-up steam engines. He now wanders the world as a freelance 'Biological Consultant,' seeking out those whose 'output' is high enough to justify the cost of his divine sutures.