The background: low-fantasy cultivation, fictional empire

The traitor Gu Mang returned to his home kingdom (country? empire) again. Everyone rejoiced in his banishment. It was said the one who hated him most was his closest friend—the cold and stoic Young Master Mo.

A rumour: Young Master Mo prepared three hundred and sixty-five methods of torture to try on Gu Mang, enough to play with him for a year without repetition.

But what's the truth then?

Well the truth is even more unspeakable—

Mo Xi's identity: the most abstinent commander of the empire.

His relationship with the traitor Gu Mang: they'd slept together before.
(Summary provided by @K.san)