Lifted from ‘http://en.wikipedia.org/wiki/Death_(Discworld)#The_Death_of_Rats‘

The Death of Rats

The Death of Rats, also known as the Grim Squeaker, is not, strictly speaking, a personification in his own right but rather an aspect of Death allowed an independent existence. His purpose is to usher on the souls of dead rodents, as well as assisting Death in other ways. His jurisdiction also seems to cover certain kinds of “ratty” humans, such as Mr. Clete in Soul Music, Mr. Pin in The Truth, and Mr. Pounder in Maskerade.

He was one of a disparate multitude of death-personifications created during Death’s absence in Reaper Man. The Death of Rats refused to be reabsorbed into Death himself upon the latter’s resumption of his duties; therefore Death kept him around for company. The Death of Fleas also escaped reabsorption, but has not been seen since Reaper Man. The Death of Rats resembles a rodentine skeleton walking on its hind legs, wearing a black robe, and carrying a tiny scythe, his form having taken shape from the latent form of Death himself in Reaper Man, as he came into existence in the vicinity of Bill Door.

The Death of Rats more easily finds ways around the Rules than Death does, and has assisted Susan in Soul Music, Hogfather, and Thief of Time. He sometimes travels with a talking raven named Quoth who also acts as his translator.

The Death of Rats, like Death, speaks in small caps, but has a vocabulary consisting of words such as Squeak, Eek, Ik and Snh, the last used when it laughs, although its speech can be interpreted from context much like the Librarian’s.