It's always settings/story dependent.
For a Dungeon story, you can expect respawning as a default for inhabitants. For a few dungeon stories, it is possible for a dungeon to earn the ability to grant instant-rezz to delvers with some limitations.
For my own work, I have established that there are rituals for resurrecting the dead, but they are difficult and expensive, and the cost is still consumed even if the ritual doesn't work.
Reasons the ritual can fail: skill issue, bad luck interruption, the person likes their afterlife and doesn't want to come back, the divinity with dominion over the soul says no, the soul is unavailable for any of several reasons. And I am sure I am missing some possibilities.
Difficulty goes up over time, as does the chances of the soul rejecting the resurrection. Also, the souls who have messed up enough to go in front of the Judge of the Dead instead of going straight to their own deity's afterlife are unlikely to be allowed to resurrect, making villainous sorts much harder to resurrect in general.
Hypothetically, if you stashed the soul of a Big Bad into a soul gem or something to keep it from heading to the afterlife, you could perform a resurrection with the soul gem present during the ritual.