This is more of a filler or natter post, but it did take me more time than it was worth to compile it.
Micahel Moorcock is one of the classic writers of the New Wave Fantasy/Scifi movement that sprange up in the 60s and 70s. So he holds a prominant place in both D&D's Appendix N and was ripped off whole-sale by Games Workshop after their contract to make minatures for the games based on his books dried up.
His most famous work, Elric of Melniboné, was a modern work of Sword and Sorcery, an anti-Conan whose terrible fate is still an inspiration for weird writing. Elric was an Eldren, a race of elf-like people who popualte the multiverse alongside humanity. But humanity is not always the same world to world. Eldren meet alll the usually requirements for being Elves but have an elaborate history that can be teased out if you pick through all the different stories. This is what I managed to compile covering decades of writing and constant jumps through time and space.
Elric being an early success means eventually the whole mythos revolves around him and his family, even if there wer extended breaks and hasty rewrites to bring it into some sort of order.
There are two races, the Eldren (created by Law) and the Mabden (created by Chaos, though how they intersect with regular humans is an untouched point). They live on the world found in the Corum series and of course the Mabden are set upon the Eldren (called Vadaugh) as part of the great Cosmic struggle. There are also the third race. Also made by Law, the Nadragh who may be related to the Vadaugh and who dwindle away after the books.
The Eldren scatter throughout the multiverse, pursued by the Mabden, many turning to neutrality, forgetting how to access the many worlds (those who remember are called Ghost People by those who have forgotten) or even Chaos. Thes Eldren are first encountered in the book The Eternal Champion by Erekosë who ends up siding with them against genocidal humanity and destroying the humans of that version of Earth. Which is very utilitarian of him as the story shows, but was just as much a subversion as Elric was.
Of course some souces like the wiki say the Vadaugh and Nadragh are descendents from the Eldren who fleed across the multivese and not the othr way around. Bu that's Moorcock's writing for you.
In the process of scattering, a contingent of Eldren women becomes embroiled in political conflicts in a nexus of 6 worlds and John Daker (Eternal Champion who is cursed to remember) incarnates as Prince Flamadin, and with anti-Nazi German army officer Ulrich Von Bek, Count of Saxony, saves the day. And fuse again the swords required to create the Black Sword (a demoic inteligence who is also a member of the Enternal Champion's destiny). This lets the dragon out who guides the Eldren woman to their menfolk elsewhere despite the many generations that have passed. Ulrich marries the Ghost Warrior Alisaard, despite the problem that Eldren and humans cannot interbreed without ‘a great deal of alchemy’, reinforced by Erenkose's, Elric's and Corum's inability to sire children with their versions of the Eternal Consort. Ulrich finds the Holy Grail, the key to the multiverse which his ancestral namesake (also the Eternal Champion) was sworn to protect by Lucifer.
The descendants of Ulrich and Alisaard migrate to a world where they are sworn to the powers of Chaos, these people who become the Melnibonéans will eventually also mate with dragons. This results in the Melnibonéans and Dragons (Phoon) occasionally giving birth to eggs/Eldren, which is explored in three of so short stories that only came out after the 90s.
These people are led by leaders who are really their future emperors dreaming/living separate lives to prepare themselves. Elric while doing dream quests lives out multiple lives in the Von Bek family, such as Count Ulrich Rudric Renark Otto von Bek-Krasny, the main villain from the Seaton Begg detective novels that Moorcock took over and rewrote into his own mythos as a Von Bek relative.
Elric will eventually fight Roland (the French hero) as part of trying to remake the world after the destruction it and the hands of Chaos and die in the final act. Before that on his adventures, he meets Oone the Dream-Thief and has a brief fling. Despite that Eldren and humans not being compatible, as seen by the sterile half-Melnibonéans slave class, but also countered by the fact Melnibonéans have humanish eyes (possibly from untold years of female Eldren/male human breeding on the 6 world nexus), Oona has twins; Onric and Oona. Oona marries Ulric Von Bek, who is an anti-Nazi German and Elric on a dream quest. This is a differnt universe Ulric Von Bek than the one who is Elric's ancestor evn while Elric occansionally possess him. It's also revealed that Elric fathered the Von Bek family on another dream quest so retrospectively gave the family a history of albinoism, which manifests in the people Elric himself manifests as. Ulric and Oona have an adopted family, including a son who has perfectly normal daughter named Oonagh. He also protects the Holy Grail, which is also the Runestaff from Moorcock's other other series, Hawkmoon/The History of the Runestaff.
Oona has adventures in fantasy North-America, with Ayanawatta (Hiawatha), White Crow (Elric on his first dream quest), Ulric and Elric (who is strapped to the mast in Stormbringer and on a dream quest via possessing Ulric again).
This all leads to a big (if rushed) adventure where Oonagh has to rescue a boy named Onric (calls himself Jack D’acre) from a big multiverse battle called the Conjunction of the Sphere, which is basically where every Eternal Champion book series ends up in the end and where Erenkose died saving Talernon the eternal city and destroying the Eternal Balance, mostly to rid himself (as John) of having to relive past incarnations.
In an alternative Granbretan where Hawkmoon is on the verge of failing (as opposed tho the Hawkmoon books where he wins), everything collides in a ritual and the day is saved. Oonagh and Onric begin a relationship (thanks to dimensional stuff they are only 6 years apart), Onric changes his name to John Daker, becomes a stockbroker and later start suffering bad dream of being the Eternal Champion. This is odd becuase the first time we hear of John Daker, he is in the 1960s and was born in WWII. Oona becomes Una Person (or maybe her mother Oone was always that), proceeds to embody the Black Sword (sometimes) and mess with Cornelius (Eternal Champion in a whole different cycle of stories).
So all very confusing. But can be summed up as interdimensional elves settle on many worlds as Cosmic Conflict keeps forcing them places so and become the local "Magic People" to enable sword and sorcery action.