One of the founders of The Outskirts and its first high shaper. He helps Cole many times throughout the 4th and 5th books.
History
Dandalus is an Echo. When he arrived in the Echolands he didn't want to leave. He found five other powerful shapers, and together they "learned how to cheat the call of the Other and used the time to grow in power. Eventually, we decided that we wanted to live again. So we used our abilities to create a material world here in the echolands. A mortal world" (4:385), which became The Outskirts (on the third try). He was tasked with physically starting the world, and thus is the originator of the Founding Stone. In these Outskirts, Dandalus became the first High Shaper. These shapers "transformed our echoes so we could dwell there [The Outskirts]. It made us feel alive again. A detailed simulation of mortality" (4:385).
When the other echoes threatened to destroy the third Outskirts, the "six of us withdrew and left mortal Grand Shapers in our place" (4:387), cutting off most contact between the Echolands and The Outskirts. They also successfully imprisoned the two torivors just before the cutoff.
Dandalus was the creator of the cloudwall in Sambria, and says it is made from dreams from all worlds.
Dandalus now remains in the Echolands. He is known as the Warden of the Light. For two hundred years before Cole Randolph arrived in the Echolands, he had had no visitors. He was in hiding behind the Pass of Visions when Destiny Pemberton arrived, followed shortly by Cole. Dandalus indicated that, once the two left, he would move to a new hiding place.
Reference in Beyonders
Dandalus may have been the origin of a Lyrian expression uttered by Ferrin the Displacer, "Great prongs of Dendalus!" This was sighted in Seeds of Rebellion, a Beyonders book, on page 273.