A duology by Diana Wynne Jones focusing on magic users known as Magids and other witches and sorcerers. Deep Secret takes place several years prior to and sets up events in The Merlin Conspiracy. Both novels are set in the Multiverse, a collection of thousands on universes in which magic is more or less present. Earth features prominently in both novels as well as various other magical worlds. Whilst each book mainly contains its own set of characters several do cross over, mainly Nick Mallory.