Hi AronRP. While most Journey Steps are now fully functional, this one is not. As TheLOLxd2 said, The Mummy of the Ring is not currently in the game for some reason. Is is possible that he will be released as add on content at a later date. I saw him on a different video by JustHorse, who told me he was spawned in manually. While it is possible to spawn him in using the admin panel, he feels very weak and unfinished, and I would strongly advise to simply wait for him to to be either added in or fixed. Me and several other players looked into the issues surrounding him in more depth on a thread we built to test bugs. You can find it here:
https://forums.funcom.com/t/attn-pc-players-testers-and-the-tech-savvy-please-help/50616
Ps- how did you manage to get ‘Ch10, Step 8: Explore the entire exiled lands’ to work for you?