The Main characters who use Death's Domain are:

Death, Susan Sto Helit, Death Of Rats & Quoth

Death

On the slightly odd and magicaly enhanced Discworld, anthropomorphic personifications take on a life (or, in case of DEATH, an existence) of their own. Death is your classic seven-foot tall skeleton with pinpoints of blue fire in his eyesockets. He is not as most people make out the ruthless destroyer of people, plants and the occasional cow, but rather a timeserver who has all Eternity to serve. He tries very hard to understand mortals, but this effort is largely negated by his utter lack of anything even remotely resembling a sense of incongruity or a sense of humour.

Susan Sto Helit

Death's Grand-daughter, Her parents were Mort and Ysabel. Susan has much the same abilities as Death such as walking through walls, using Death's voice and she can move through all the moments between thoughts. Two of the most noticable things about Susan are: her hair and her birthmark. Her hair is white apart from a black streak running down the middle and it manages itself. Her birthmark is white and when she blushes you can see three white lines running down her cheek as if she'd been slapped. When she gets angry however these lines start to glow.

Death Of Rats

Much Like Death but smaller and rat shaped. The Death Of Rats came into exhistance when Death was made to Retire. After Death killed the new Death, He recalled all the Death's that had been created to take his place, only the Death Of Rats didn't cause he held onto a post and didn't get sucked back to Death. His speach looks like this"SQUEAK".

Quoth

Quoth is a raven. He is often used as transport by the Death of Rats and they seem to have become rather good friends. He is a rat to human interpreter when Death Of Rats is tryin to communicate something to Susan as she doesn't understand rat.