Firstly The Source, aka: The Source of all things, the creator, the first, the ageless, the infinite. He created the otherworlds. The rest is mysterious. ie. We don't know. However we know he created the titans and the ancients.
The Ancients are Ani, Morr, Wyrd and Hojo. They are the ancients of life, death, order/destiny and Chaos respectively. It is not so much that they are for those things, as much as Ani defines the characteristics of life. Death is death, because it is Morr's domain.
The Titans are also four in number, one dedicated to each element. K'z'k is the titan of fire, Sharna of water, Gorim of earth and Aegia of air. They are not so much defined by their element so much as they define the element. Fire is hot and burns stuff, because K'z'k personifies those traits. K'z'k is wild and violent, and very destructive. He is the fastest to anger, and takes the longest to calm. Sharna is moody and tempermental, and will also anger quickly, but will collect herself and calm just as quickly. Gorim is slow and ponderous, his temperment like stone (or more correctly stone resembles his temperment). He won't anger quickly, but when he is moved to violence, his wrath is an avalanche of implacable fury. Aegia is often depicted as his wife, and is fickle but not prone to violence.
The Eldar Gods are the gods of the elves, trolls, giants and dragons. They express loose groupings of moods and concepts, as they were created by the concentration of these concepts. Typhil, Eldar of sickness and disease for example is famine, illness and blight personified in a deity. His bloated body sits upon a throne of petulant corpses. He is attended by rats and the very ill. He was created by the collective thoughts of sickness, and as sickness spreads his power waxes. Nympus, Eldar of beauty however is a seductive queen with a body so perfect that all lust for her. She is called upon to bless children so they grow to be attractive, and her domain is over all things of beauty. As the old races, and the young races were spawned they also preyed to these gods.
The Old Gods in contrast are the gods created by the dwarves, gnomes, fayrie and meyr. They are created in much the same way as the Eldar Gods, but they are more focused. They are pantheons unique to each race, and they have complex histories fueding with other gods, fighting mighty beasts and banishing demons. The Eldar races never had gods in this fashion, as they each prayed to the Ancients, and the Eldar gods for protection. An example of this is Havestos, dwarven god of the forge.
The Young Gods make up massive and complex pantheons that are constantly in flux and the god's powers wax and wane. These gods are common, and are usualy much less powerful then the old gods or the eldar gods. However, they tend to take a much more avid interest in the life and day to day existance of mortals. This is as their power is in direct proportion to the amount of faith their followers have in them. These gods are constantly at war with eachother, and many are dying as their followers are put to the sword, their shrines torn down and their names forgottern.
The Dark Gods are a subgroup of all the gods. They are the negitive, evil gods, who are evil by their very nature. They are numourous and all bare only one common trait, being malicious in intent. They themselves are the product of evil deeds and thoughts, they will often work with and against eachother. They are lead by the Eldar God Malik, god of evil. Underneith him are the seven sins. Each one of the seven are gods dedicated to a sin.
- Lucifer: pride
- Mammon: greed
- Asmodeus: lust
- Levian: envy
- Beelzebub: gluttony
- Amon: wrath
- Belphegor: sloth
The Spirit Gods are created by ancestor worship, by praying to the spirits of the dead they become a type of minor deity. They are weaker then most the other gods, but they are much closer to the mortal plane, and will frequently take a hand in what happens. They can be like a kind of gaurdian angel for their decendants, giving them luck and strength when needed.
The Chaos Gods were created by Hojo, they are a caste of gods designed to keep the world in a constant state of flux and flow. They were the original gods of the orcs and the beastmen. However, by their very nature they won't remain worshipped by any group, their fickleness means they make poor gods, and they usualy forget their charges and find new ones. They don't even have permanant names or identities - at times there is one, at other times there are an infinate pantheon of them warring with everything and everyone. Or not, just to mix things up ;).