The following hints should provide enough nudges to solve Roger Zelazny and Jane Lindskold's challenging and fun science fiction puzzle-adventure about pocket universes.
Pocket universes are fantasy-island type solar systems carved out of space by imaginative designers.
You find these Keys with the aid of a Direction Finder, after first going to Magnetic North in each universe and activating the Resonance Tracer. Someone has been turning off their keys, leaving the universes suspended in time, like Sleeping Beauty's castle. You are Korda.