One of my all-time favourites manhwa Shin Angyo Onshi – a collaboration between 2 korean manhwakas – Youn In-Wan & Yang Kyung Il.
Story : In an ancient kingdom of the Far East called Jushin, there were secret agents called Angyo Onshi, or Amen Osa, and with the power imbued in their Mahais, they were able to summon armies of soldiers to their aid. But Jushin has fallen into ruin. And left only one man – Munsu, to bring justice to the country and to seek the very one man who destroyed everything….Will he be able to bring that man down? What are the chances of winning against a supernatural evil?