Discworld's Death is a parody of several other personifications of death. Like most Grim Reapers, he is a black-robed skeleton carrying a scythe and, for royalty, a sword (It's the rules, he once told Mort). Unlike many of them, he has a personality beyond this.
Death is one of the most popular Discworld characters and makes an appearance in every Discworld book except The Wee Free Men. His steed is a great pale horse called Binky who is very much still alive. His hollow, peculiar voice is represented in the books by unquoted small caps; it is peculiar because since he is a tall skeleton, he has no vocal cords to speak with, and thus, speaks through other means. In The Colour of Magic (the first Discworld novel), and in
Faust Eric, all direct written references to Death are proper nouns, thus, for example, "he" is written as "He". This is usually reserved for the Discworld gods and is not featured in any of the other novels.
Death is not invisible. Most people just refuse to acknowledge him for who he is, unless he insists. Under normal circumstances, only those of a magical disposition (e.g. witches and wizards), children and cats can see him, or allow themselves to see him. Death can of course ignore things like walls or magic spells that stand between him and his object: this is because he's much "realer" than they are. A castle might stand for centuries, but Death has existed for billions of years: to him, the walls of the castle are less substantial than a cobweb. However, he can only go where people can die, as shown in Hogfather.
The Streets of Ankh-Morpork was the first of the Discworld Mapp series, and features an atlas of the city of Ankh-Morpork, the rich, powerful, and sprawling city in the Discworld series.
The map was devised by Stephen Briggs, who compiled references from the Discworld novels, and revised it many times with test readers' help. Terry Pratchett also checked the many revisions of the map, and was very surprised at how well the city fitted together. In the accompanying booklet he said that he thought Ankh-Morpork was unmappable, as he'd made it up as he went along, but that he then realised that real cities are also made up as people go along. Pratchett later revised his above opinion, saying that a fantasy world should not be mapped until it has become established in the creator's mind. He had expected a map to restrict future ideas, but found instead that it inspired them.
The final, artwork-grade map was drawn by Stephen Player, who also drew the artwork for a later publication, The Discworld Mapp. The Streets of Ankh-Morpork, an aerial-view map of the city of Ankh-Morpork, looks vaguely like a brown and green cut onion with a river bisecting it. An enclosed booklet includes Pratchett's and Briggs's words on how they devised this map, and a 6-page map legend listing the many famous and picturesque establishments in Ankh-Morpork.