An important subsidiary character in The Ballad of Adler Young.
MacFogg was a servant in the Royal Palace, when she seduced (or was seduced by, or possibly both) a grieving King Gawain Adlersson. Gawain, who was in a deep depression over the disappearance of his mate, Queen Persephone, fathered upon MacFogg a bastard, named Adler.
As a mother of a royal bastard, MacFogg was quietly banished from the Royal Court, but not left destitute. She was allowed to raise Adler Gawainsson quietly and without interference.
Most importantly, MacFogg appears to have been a member of The Sisterhood, a somewhat shadowy organization devoted to restoring the vigour of the Elven Race. MacFogg raised her young skunk-kit in ways designed to fulfill the objectives of The Sisterhood, including making him a strong and talented magick-user.
At one point late in Adler's youth, the Ferifax Arch, a scheme designed to destroy the Elvishness of certain changelings, was destroyed, and the resulting investigation induced Mavis to flee the Empire, and possibly Faerie, much to the distress of Adler. Her subsequent whereabouts are unknown.