First and foremost would be the Lord of Nightmares, or L-sama. She created the five worlds, including the one the Slayers takes place on and the one of Lost Universe, Hajime Kanzaka's other creation. On each of these worlds she created two major races - the mazoku (or Monster) race and the Shinzoku (or race of gods), as well as humans and ryuzoku (race of dragons, Golden, Ancient, Black, etc.).
The Shinzoku include Vorfied, the gaurdian of the Lost Universe world, Cefied, the Guardian of the Slayers world, and two others who are unknown. The purpose of the Shinzoku is to counteract the destruction of the mazoku.
Vorfied is the Night Dragon God. He battles against Dark Star.
Cefied is the Flare Dragon God. He battles against Ruby-eye Shabranigdo. In fighting Shabby during the Kouma War, he used up all his power and has ever since remained dormant. Like Shabranigdo creating five mazoku lords from himself, Cephied created four other Dragons after said incident. At least one piece of him exist in a human though, who is known as the "Knight of Cefied", Luna Inverse, Lina's big sister.
The other Dragon Gods are unknown, though they fight against Chaotic Blue and Death Fog.
The Dragon Kings that Cephied creates are:
Rugradia, the Water Dragon King. During the Kouma War Rugradia used up all their powers in sealing Lei Magnus, or Shabranigdo's current carrier, in a block of ice, where he still lies in some mountains up in the north (please tell me if you know the name ^_^;;). Rugradia also used all his powers to seal Chaos-Dragon Gaav away inside a human body. His knowledge is sealed in the Clair Bible, and his remaining thoughts in the form of Auntie Aqua, a cute little old lady from a temple and up in the Kattato(?) Mountains. He guards the West . . . I think.
Valbazard is the Fire Dragon King. I'm not sure of much about him, other than he's the Dragon King who Filia's a priestess of. I think he guards the North.
Langould is the Earth Dragon King, and guards the South.
Valwin is the Sky Dragon King, and guards the East. And he has a really cool name.
Each Dragon King has a Golden Dragon serving under them. Rugradia's is Milgazia, a Dragon who leads Lina (and Martina . . . ) through another dimension to see the Claire Bible. He's the only one who I know of.
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The purpose of the mazoku is to, pure and simple, destroy. They feed off pain and suffering, both of others and themselves. I believe that the reason behind this was that from conflict arose creation. Such as when Xellos got Martina t travel with Lina - it turned out to be the arrogant princess who got Lina to take action in the last episodes of Next. That said. . . . . .
There are four Dark Lords of the Netherworlds after the Lord of Nightmares: Ruby-eye Shabranigdo, Dark Star, Chaotic Blue, and Death Fog. Nothing is known about Chaotic Blue and Death Fog though. Dark Star fights against Vorfied in the Lost Universe world, but not a whole lot is known about him, and I'll cover that later.
Ruby-eye Shabranigdo is the Dark Lord of the Netherworlds that fights against Cefied. Long ago, though, Cefied managed to split Shabranigdo up in seven pieces, but he still didn't die. The pieces of him were then reborn in a human, over and over, until he found one suitable to carry out his rebirth. Around a thousand years before the time when Slayers takes place was the Kouma War, when this happened to one of the seven pieces - see the Kouma War section for a more thorough description of what exactly happened. He also created from him the Dark Lords of the Slayers world, who help him in destruction as well as keep up a magical barrier to keep the Dragon Kings from lending their power to humans.
Hellmaster Phibrizzo is the most powerful of the Dark Lords. He lives and maintains the barrier in the Desert of Destruction to the East. More on him in the Phibrizzo section.
I don't know if Hellmaster's priest and general are ever mentioned by name in the novels, but I think they were killed off during the Kouma War. That's why he 'borrows' Xellos in Next. Either way, they don't show up in the anime.
Dynast Grausherra is the third most powerful Dark Lord, and lives in the Northern Footholds. More on him is right here.
General Sherra serves under Grausherra, both of whom only appear in the novels. A page to her is here. He also had a priest named Grau and another priest named Norst.
Greater Beast Xellas Metallium is the either fourth or fifth most powerful. She keeps up her portion of the barrier from Wolfpack Island in the South. More on her in her section.
Xellas' both general and priest is Xellos. After the deaths of Gaav and Phibrizzo, he becomes about the sixth or so most powerful being in the Slayers world. Go Xellos! More on him here.
Deep Sea Dolphin comes just before or after Xellas in power. She keeps up her part of the barrier from the Demon's Ocean in the West. It is unknown as to whether or not she has either a general or a priest. More on her is here.
Gaav is the second most powerful of the Dark Lords. The reason I stuck him down here is because, unlike the others, he doesn't maintain a part of the barrier. During the Kouma War he was the one who Shabranigdo used his power through, so he didn't just stay any one place. More on him coming soon.
Gaav's general is named Raltark and his priest is Rashart. They never appear in the anime but come in in the novels and get killed off. He's also responsible for poor Valgaav getting turned into a Monster and all. Also, Seigram, who was originally serving under Xellas, deserted to work under Gaav instead.
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Wow . . . that's a lot of corrections! **blushes** Whoops, sorry everyone! Anyway, I'm still not totally sure if that's all 100% right, so if anybody has any corrections or information to add, please tell me!
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