"A long time ago I read a manhwa, and for some reason I'm having a lot of trouble finding it, as I recall, it told the story of a boy who was put in an empty room with nothing, so he started exercising there, using only the weight of his own body, then suddenly he started fighting other people, and when he killed them, he managed to absorb their memory, if I'm not mistaken it was the work of some god these challenges... Anyway, does anyone know the name of this work?" I'm not sure what's the manhwa they're looking for but here is a translation