During the Cataclysm, he was working on a machine that could momentarily change the magnetic poles of the world. He discovered that the machine also confused Connor's map into believing it was in the Barren Region.
The machine required a Lodestone to power it properly, and the Sage Gnome thought it highly unlikely that one could be found. Nontheless, Connor uncovered one and brought it to the gnome. After putting the stone in place, the Sage Gnome was able to use the machine to transport Connor up to the surface of the Barren Region.
The Sage Gnome is a character in King's Quest: Mask of Eternity.