I love the folkloric background that's inspired the world to begin with. If you haven't read The Folklore of Discworld by Terry Pratchett and Jacqueline Simpson I really recommend it because it gives tons of info about the type of lore Pratchett was inspired by to create all the species and myths he's put into Discworld as a whole. It was my absolute saviour when I did my research report on Pratchett.
In creating the concept of the Discworld Pratchett talks about old Indian and Hindu theories and myths:
'the age-old epic poems of India declare the world to be a disc' (p. 23 The Folklore of Discworld)
There are myths of four great elephants guarding the disc or it is one great elephant that the world rests on, who is also standing on the back of a tortoise. I loved how Pratchett took this research and blending them together to get his own Discworld. The fun about lore is finding legends and myths from all over the world that are quite similar and bring them all together to create an entirely different myth of your own.
When I was doing my report one of the books I studied and discussed was Lord and Ladies. One my favourites reading about. In Discworld the elves are evil and threatening, just the way they used to be according to Pratchett. Rather than going by modern legends that elves are mischievous but helpeful little sprites Pratchett goes for older legends where the elves and fairies tricked people into their deaths. With all the parody and comical characters like Nanny Ogg I like that little bit of darkness to Discworld. It's not all silly and humorous. There are actual dangerous things lurking around in Discworld. It's a fantastical world but keep your eyes open if you're wandering around!
I honestly admire the detail that's gone into every inch of creating this world. Every area, the seas... I wouldn't know where to start with world building.