Demonology D-E-F

Darklighters
Dark Priests
Demon Kids
Demonatrix
Demonic Waste
Devlin
Dragon Warlock
Drasi

Eames
The Evil Enchantress
Evil Spirits
Executioner Demons
Familiar Warlock
The Four Horsemen of the Apocalypse
Furies

Darklighters
The evil counterparts of whitelighters, with the only means of killing (future)whitelighters. Darklighters wear a crossbow, with deadly arrows with a point tipped in a poison that is fatal to whitelighters.
There are different forms of darklighters. One form attempts to spread evil through propagation by seducing young women and impregnating them with evil spawn.
Another form are known as 'spirit killers'. These go after people who's destiny it is to become a darklighter. By reading their thoughts and fears, they make the future whitelighter think they are responsible for everything unfortunate that happens to anyone near them, slowly driving them to despair, eventually making them so unhappy that they commit suicide. By committing suicide, the individual is denied his or her future as a whitelighter after death.
There are also 'Trackers'. A Tracker is a breed of darklighter that targets whitelighters on the verge of losing their wings. Trackers' poisoned arrows are more potent and kill more quickly.
Dark Priests
A dark priestess can bestow great power upon those who she binds as husbands and wives. Dark prriests use a dark binding ceremony to overwhelm good beings with evil and by that turning the whole family line evil with him/her. Dark priests have the ability to cloak their activities, because they need privacy in performing their rituals.
Dark priests also perform rituals as weddings and dark coronations.
Demon Kids
They look small and innocent, but in fact, Demon Kids are very dangerous and impossible to vanquish. The only thing that can destroy them, is the Nothing.
Demonatrix
A group of deadly female demons, assasins. They're famous for their weapon choice; a throwing star. Demonatrix' can teleport and have excellent fighting skills. They can be vanquish by their own weapons.
Demonic Waste
When a demon is vanquished, some energy still lives. When many demons are vanquished in a common area, it could happen that the demons' residual energy may coalease and form malevolent manifestations, which may perform simple pranks like moving objects, but may grow strong enough to pose a treath.
Devlin
A warlock. He stole the muses' 'Ring of Inspiration', so he could trap muses and use their inspiration to give to other demons working with him, so he could eventually take over the underworld.
Dragon Warlock
Perhaps the most feared and Powerul Witch Killer there is.

Fear His Flight
Fear His Fire
The Strength Of
A Hundred Men

Lineage: The Twisted spawn of a Dragon and Sorceress. Beware: Only the Most Powerful Dare Challenge.
Drasi
The demon of hate. He fell in love with a mortal woman. When Cupid found out, he redirected her love to keep her from being harmed. Drasi got mad, and stole Cupid's ring, to conjure up hate in people's hearts, causing Cupid a lot of pain and if he would continue, causing him to eventually die.
Not only does Drasi kill someone's love but can inevitably destroy someone's ability to love.
Eames
In 1991, Eames murdered a witch in Glasgow, Scotland, and stole her cloning power. In 1989, Eames killed a witch in Nairobi, Kenya and stole her power of transmogrification. Besides these, he controlls fire. This makes him a very powerful warlock, and so all witches should consider him to be a serious threat.
The Evil Enchantress
As one of Paige's past lifes, the Evil Enchantress was defiant, clever, and indepent. The Evil Enchantress lived many centuries ago in the Middle Ages. She came late into the craft, but learned it quickly. She had the power to control the elements. The Evil Enchantress cast a spell upon a prince so he may marry her, so she could take over and rule his kingdom. Once her child would be born, darkness would rule the kingdom, and the world would be covered in darkness too.
Evil Spirits
Evil spirits are ghosts that remain in our world by hanging on to some unfinished business, generally revenge. Unlike other ghosts, evil spirits' intentions are to harm living beings.
They can only be vanquished on the astral plane. The vanquishing spell has to be read by someone else's spirit.
An other way to vanquish them is to spread a potion over their bones, or destroying the object of the spirit's wrath.
All ghosts leave ultraviolet fingerprints, because the ectoplasm that composes ghosts' skin is out of visual spectrum.
Executioner Demons
Executioner Demons are minions of a low order. They are incapable of such as original thoughts or deed. Usually they're found in the employ of either higher level demons or mortals proficient in dark arts. They're vanquishable with own weapons or a spectrum of valerian potions.
Familiar Warlock
When a new witch's animal guide, her familiar, betrays her or him, it turns into a warlock. If the familiar can shed all of its animals lives before the next full moon, it becomes immortal and along with that of course impossible to vanquish.
The Four Horsemen of the Apocalypse
Four horsemen, handpicked by the Source himself, the 'Annointed Ones'. They bare the mark of the omega; the end. The horsemen each have their own 'specialty'; there's Strife, Famine, Death, and War. They use their powers for spreading loss and death in order to lead to the eventual destruction of the world. They're immune to all magic, and only the Source can vanquish them.
When a team of horsemen fails, the Source vanquishes them and picks a new team.
Furies
Just like their mythic ancestors, these demonic women called Furies act as judge, jury and executioner to anyone they consider an evil doer.
Furies kill the evil doer by letting them inhale their smoke. When someone good inhales the smoke, it looks for a portal of unexpressed fury. It builds until it consumes your humanity and turns you into a fury.