Jagwi is a subordinate of Bigak. His reputation among other chachaoongs is very bad and he has been in hiding for years out of fear that Cheoyong would find and kill him. He is mostly known for finding young chachaoongs and maiming them in some way (such as removing their eyes or ability to speak like with Hiljo and Haje), then placing a deadly mark on their body, forcing them to serve him. Most of his servants die in horrible ways, according to Hiljo, and it is implied that Jagwi is exceptionally cruel to them. Any who disobeyed had their marks activated, and were killed.
It is unknown what his goals actually are, but he is finally stopped after an awakened Yu Jin removed his left arm and sent him running. After being found by Cheoyong, he was taken away to be tormented for his crimes, as killing young chachaoongs is against Jack's rules.