
I believe that that Guwon is Sisyphus in a very real sense. Part of his legend involves him tricking Hades into chaining himself to a rock in the underworld which lead to a 'no more death' situation (like we see in the beginning of the manhwa - people can't die anymore). This then pissed of Ares because none of the people he was fighting were dying, so someone figured it out and unchained Hades, then they punished Sisyphus by making him roll that boulder up a hill for eternity.
There are also a lot more references to his muscles being "hard as a rock" and the fact that he's extremely cold (like a rock). The first time Jinwoo walks to Guwon's house he comments on the incredible number of stairs saying "Why would anyone want to climb these stairs that seem to go on forever??" - Someone who has been pushing a huge boulder up a steep hill for who knows how many centuries, that's who!
There's more too, I can keep going if y'all would like!
I've been researching (cuz I love to), and Sisyphus was a king in Ancient Greece who was punished by Zeus and Hades, forced to push a boulder up a hill for eternity only for the boulder to roll back down to the bottom where he'd have to start all over again.
** In chapter 1, amid the chaos we see Guwon's hand reaching up from under the ground, like he's crawling out of Hades/Hell
** In Chapter 3 Guwon takes Jinwoo on a hike to a very remote place to stare at a boulder on top of a mountain, then says "What if it moved and crashed back down?"
Very clever Author-Nim! I'll share more notes as I find them - I started re-reading to make sense of it all and I've already got quite a bit (๑•ㅂ•)و✧