I'm confused on the relationships between Raven Queen and Myrkul. They sound like they have a very similar job description – they both are the one you see when you die, and they both like to scare people about that.
Can there be two gods of the same domain? Perhaps Raven Queen takes elvish dead and Myrkul takes human dead?
(This is specific to 5e)
Best Answer
Only Myrkul or the Raven Queen can be a deity at the same time, depending on the setting/pantheon - in the Forgotten Realms, it's Myrkul (replaced by Kelemvor)
All of the information I know of about Myrkul can be found on page 35 of the Sword Coast Adventurer's Guide (this is just the first paragraph):
So it seems as though Myrkul was the god of death, but then was killed, and Kelemvor took over. Then he came back, but didn't really reclaim his previous title; instead, he seems to be an intermediary, claiming souls and delivering them to Kelemvor.
The Raven Queen, on the other hand, is a bit more ambiguous. In the Dawn War pantheon (listed in the DMG, p. 10), she was the goddess of death. The Dawn War pantheon is not the same as the Forgotten Realms pantheon, so I guess there is no Myrkul when she is the goddess of death (as part of the Dawn War pantheon).
In the Forgotten Realms, the Raven Queen is not the goddess of death, but is instead something else. Taken from Mordenkainen's Tome of Foes (p. 58):
And from page 60:
This, in the context of her origin story on page 58, suggest that she tried and failed to become a god, which is why she has earned the enmity of Corellon and Lolth. She is now just a "quasi-divine entity", which says to me that this is not a "true" deity like Myrkul.
On the other hand, it does say "divine" again on page 58:
However, given that she was already described as a "quasi-divine entity", maybe this isn't as interesting as I thought, but I included it for completeness, at least.
So my conclusion is that Myrkul or the Raven Queen is the god(dess) of death depending on whether you're using the Forgotten Realms deities or the Dawn War pantheon. If the former, the Raven Queen isn't actually a true deity, so that would make Myrkul (and Kelemvor) the deities related to death.