Death (Discworld)
Death has appeared in every Discworld novel, with the exception of "The Wee Free Men" and "Snuff", and had a possible cameo at the end of "Johnny and the Dead" (the character was not identified, but spoke in unquoted small caps). The Discworld books with Death as a leading character, starting with "Mort" in 1987, are:
Death (Discworld)
Death has developed considerably since his first appearance in "The Colour of Magic". In this, he was quite a malicious character and follows Rincewind around wanting him to die after circumstances resulted in Rincewind 'missing' their scheduled 'appointment'. At one point he deliberately stops a character's heart, though this may have been Death's stand-in, Scrofula. By the time of "Mort" he had gained the sympathetic and humorous personality he has in later books. In later novels, he has been used to examine developments in theoretical physics as, being supernatural, he is able to witness such events firsthand, although being a cat lover, he is not fond of the Schrödinger's cat thought experiment, believing it cruel to the cats involved.