I thought that the well god's reaper friend just made himself look like Jaheon so Muhan can reach Nirvana more comfortably and easily(?). Lowkey feel Muhan noticed what they were doing but knew the intention behind it so he didn't say anything in the end and followed quietly cuz like... He made A face— ngl it kinda felt like he didn't wanna go and wanted to go to Jaheon instead but he knew he didn't have the power to, and instead of kicking up a fuss he decided to go instead so the Mugos can resurface and save Jaheon in his stead. (Overthinking much? It was just 2 panels xD)
Anyway... Reapers are known to take the form the soul likes most, and since we have modern Jaheon alive the reaper can't be him cuz his soul got reincarnated.

Those cuties were centipedes...soul of the centipedes that Muhan had to consume... VENOMOUS CENTIPEDE!! God, imagine having to see them everyday and remember that you had to fight them to survive.
And awww, Muhan finally got his nirvana. Jaeheon came for him. And Jaheon currently is 20 so I knew it!! Poor Muhan wasn't even 20 yet when he got brutally murdered for the sake of the curse. I wonder what will happen to Lord Mugo now that Muhan's soul has departed. Are all the Mugos one entity now?