Hiergargo was the magician who created the Hollow Tube through the Earth.
He was a subject of Tititi-Hoochoo but was also a great traveler. He built the Tube in the Year of the World 19625478 to facilitate his journeying, but when he first used it, he tumbled through the Tube so fast that he shot out the other end and struck a star in the sky, which exploded with the impact. (Tik-Tok of Oz)
In the books of March Laumer Hiergargo becomes a significant presence.