This topic may contain spoiler
I've told a lot, so if you want the simple answer just read the first words
In this fight, jinwoo will die, but he will meet the previous monarch who instead of taking his body, he will give jinwoo all his power. He's going to say something like he's finally going to die and I don't know what. After that, the MC gets to be very powerful, and the system's going to kind of disappear. After jinwoo wakes up the king of beasts practically runs back to his home in fear, believing that the original monarch has returned. However jinwoo goes after him and kills him.

quite sad that he will die, but wasn't he supposed to help with some gates that were actually his past shadows and all? it's been quite some time since i've read the novel so maybe i'm mixing the arcs? oh, and don't worry, it's the main character, he can not really die, you know