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:
Discworld (world)
In the opening books, the number eight is generally significant and has magical properties on the Disc, (e.g. the number of the colour of Magic, octarine) and should never be spoken by wizards especially in certain places. Doing so may allow the ancient dungeon dimension creature "Bel-Shamharoth the sender of eight" to break through (this is taken to a somewhat extreme end in one book, as even the "narrator" takes great pains to avoid saying the word). On the other hand, eight turns up in many places one would expect the number seven in the real world (e.g. the Discworld week contains eight days, not seven). After "The Colour of Magic", both the colour and the number eight no longer appear as dangerous.