How many I approach this without giving spoilers?
Elric, the last emperor of Melnibone'.
Set in a world before the Hyperborean world of Howard.
Long before the first rise of Atlantis.
A world in which the race of men were just beginning to rise and the multi millennia long reign of Melnibone' was fading.
A world of magic, caught in the endless struggle between the forces of Law and Chaos.
The Melniboneans were not human.
Their origin unknown.
Dragon riding sorcerers, Allies to Arioch demon god of chaos.
My best attempt to describe them,
Elves of Chaos and evil.
Elric, the last emperor, of the fading empire. The first to be born, with a crippling birth defect.
A conscience.
An Albino, sickly, weak, with a conscience. The complete antithesis of his race.
Caught between his conscience, the struggle of law and chaos and the betrayal of family and his people.
Elric carves his way through the world. Never desiring to be a warrior, a hero, a champion.
Yet led inevitably into those roles by his conscience.
There is no way to discuss the epic tragedy of is life without significant spoilers.
Suffice it to say, it is tragedy that would shatter the strongest, yet forged a weak, sickly albino into an avatar, the avatar of the eternal champion, a champion that battles against the evils in both law and chaos, serving to maintain the balance that allows the existence of life. All, nearly accidentally, all byproducts of the inner struggles of Elric and his conscience.
Elric has left significant impact on the world of fantasy.
George R.R. Martin clearly based his Valyrians upon Moorcocks Melnibone'.
The Witcher, was derived from Elric, the albino wanderer, magical, dependent upon special magical potions to live, called The white wolf, all directly incorporated into Garalt, the Witcher.
Elric has been a favored subject in music as well. From the Hawkwind -Moorcock collaborations, To Blue Oyster Cult, to Domine, Blind Guardian, Cirith Ungol, etc.
The Elric Books are must reads!
Start with,
Elric of Melnibone'
Here is my favorite Elric song.
Written by Michael Moorcock and Blue Oyster Cult.
https://www.youtube.com/watch?v=k3nTaL31OkU&pp=ygUzdmV0ZXJhbiBvZiB0aGUgcHN5Y2hpYyB3YXJzIGJsdWUgb3lzdGVyIGN1bHQgbHlyaWNz
Saying Geralt was "derived" from Elric is the polite way of putting it.
Moorcock's influence on speculative fiction writing is immeasurable...