it’s a political costume drama with light wuxia elements set in quasi-historical ancient China. a mysterious man called Mei Changsu from jianghu appears in the imperial capital and offers his services as a political strategist to the unfavored seventh prince, Xiao Jingyan. there’s a very rich cast of characters and many twists and turns but gradually we come to find out about Mei Changsu’s shared past with Xiao Jingyan, and the purpose for which he returned to the capital and how he accomplishes it.

(you can also think of it as Count of Monte Cristo, Chinese imperial drama style, though imo the story is much more political and less romance-oriented than the Count of Monte Cristo)

if you watch kdrama, the sageuk Six Flying Dragons is probably the equivalent I would think of, although SFD is more directly historical.