Acathla - BtVS season 2 - The how in Angelus’ plan to destroy the world. Removing a sword from it’s chest would result in the world, and everyone on it, being sucked into hell.

Adam - BtVS season 4 - Maggie Walsh’s pet project. A demon/human/cyborg hybrid intent on remaking the world in his image, starting with the soldiers in the Initiative.

Anyanka - BtVS season 3~7 - The Patron Saint of Scorned Women, this vengence demon was called forth by Cordelia after a nasty breakup with Xander. After a few years as a human, Anya is currently back doing teh vengence thing as a retaliation for Xander leaving her at the alter.

D’Hoffryn - BtVS season 3, 6 - Anyanka’s boss. Can turn humans into demons.

Doyle - AtS season 1 - A Bracken demon, Doyle was Angel’s first link to the PtBs. Cute, Irish, and dead before the end of the first season. Bad Joss.

First Evil - BtVS season 3 - A supposedly very big bad that tried to get Angel to dust himself.

The Gentlemen - BtVS season 4 - Pasty, floaty ghouls who robbed the residents of Sunnydale of their voices, and then tried to do the same thing with their hearts.

Glory - BtVS season 4 - A Hell God who had been banished to earth. Also known as ‘The Beast’.

Kathy - BtVS season 4 - Buffy’s first soul sucking college roomate.

Order of Taraka BtVS season 2 - Deadly assasins

The Scourge - AtS season 1 - A pure blooded demonic hate group that targets half breed demons and humans. Was responsibel for Doyle’s death.

Vampires - The lifeblood of both shows... kind of.

Whistler - BtVS season 2 - A Balance demon. His mission is to even things out between good and evil. Played a major role in Angel’s transformation into the well coifed bloodsucker we all know and (some of us) love.