Mind the psychological tag. We spend a lot of time in the main character's thoughts. When Caden dies, in an accidental fall, he is merged with a dungeon core in another world. He's not particularly happy to be dead, so resurrection in any form isn't too bad. The real problem? The dungeon core wasn't dead, and he has to share mind-space with it. And that doesn't take into account mastering his new abilities well enough to escape from the powerful wizard that is, understandably, leery about all...

The new version of this is available here: https://www.royalroad.com/fiction/40181/saga-of-the-soul-dungeon When Caden dies in a car crash he is put in a dungeon core in another world. The problem with that? He still has a conscience, but the original dungeon core is still there in his mind, and it doesn't... Of course, other people add their own issues: Two human nations gain access to the dungeon and are not particularly pleased to share. A sentient plant race claims the dungeon as sacred g...