The Dour Dryad and the Blue Fairy are creatures that live in the woods at Briones Park. They like to live in trees. The Dour Dryad is along the Spengler trail, and the Blue Fairy is along the Alhambra Creek Trail.
To find the Blue Fairy, take the narrow trail just to the south of Alhambra Creek trail, which is just on the south side of the Creekbed. (You can cross back and forth between these in a few places if needed.)