King of the Elves
The King of the Elves lives in a parallel (and parasite) dimension, one of whose entrances is found below The Long Man in Lancre. He is summoned by Nanny Ogg to put an end to the viciousness of his wife, the Queen of the Elves. He is described as being similar in appearance to a human, but with a stag's legs and giant antlers. Oh, and a certain other accessory that makes Casanunda the dwarf's mouth drop wiiiiiiide open... This physical appearance recalls the Horned God of old pagan rituals (surviving as Herne the Hunter, not to be confused with the Hunted). Old gods were often associated with fertility, so he "Doesn't half look like his picture". As Witchcraft (wicca) is often said to be a survival/revival of these old cults it makes sense for the King to describe himself as the God of the Witches (while deploring Nanny Ogg's lack of reverence). Of course the new-age witches in the Tiffany Aching stories have pictures of the big horny blighter on their walls.
His appearance above the skyline of Lancre towards the end of Lords and Ladies ends the Queen's plans for a takeover of Lancre.
In the The Wee Free Men, the Nac Mac Feegle tell Tiffany of how the King used to live in Fairyland with the Queen and it was summer time. Then they had an 'argument', the sort of magical argument that led to mountains being destroyed and hundred dead. After that the King left Faiyland, and it became a land of winter, reflecting the cold mood of the Queen. Soon after that the Feegles left as well, 'due to the tyranny of the Queen' and certainly not because they were found drunk at 2 o'clock in the afternoon.
On Roundworld, the King of the Elves is Oberon, who fought with his queen, Titania, and just as here, was able to defeat her without much fuss. Although she is the louder and more prominent in both partnerships, it didn't take much for them to be cowed into submission.