The MC in this story is named Yeon Gaon, who has the power of The Titan's Mantle.
The Titan's Mantle is a physical force multiplier. It does not use Qi, but it multiplies Gaon's base physical attributes (strength, speed, and muscle density).
At his base state, he looks lean and ordinary. At lower scales, his muscles become slightly more defined to handle daily tasks. Pushing higher makes his body heavily muscular and dense enough to block swords. Going past scale 50 transforms him into a huge titan, causing extreme stamina drain.
Example:
Base mode (not using power) He is ordinary.
Scale up 1 time He becomes an average human.
Scale up 2 times He becomes above human.
Scale up 3 times He becomes even stronger physically, gains the ability to see fast movements, and has a larger stamina pool.
Scale up 4, 5, etc. Until scale up 50, where he becomes a titan.
He can choose whether his body looks ordinary or above human. Most of the time, he uses the scale 1 body even when he scales his power up to 10 times, simply because it is a good fit.
Rationing: If Gaon is exhausted (e.g., 10% stamina left), scaling up to Scale 10 only brings him to 100% of a normal human's capacity, not a fresh 1000%.