The Sign of the Moonbow is a novel written by Andrew J. Offutt. It was first published in 1977.
Having travelled far and wide, Cormac mac Art and Wulfhere Hausakluifr have finally imprisoned the undying sorcerer, Thulsa Doom. The two heroes suspend him from the mast the ship, finding it is the only way in which he cannot use his magic; but still, he lives.
Bas the Druid soon unveils a prophecy that may change that. They must find a crowned woman and place in her hands the skull of the undying wizard, if the mysterious curse is to be lifted.
All seems well as they set out to find this prophesied woman. But disaster strikes as the evil wizard, unable to escape his fate, vanishes into another dimension - taking the ship and his captors with him...
Cormac and Wulfhere, along with their companions, must find the way to the only person who can destroy Thulsa Doom.
But will they ever find their way home?
Encountering far off lands, hidden places, and captured queens, The Sign of Moonbow follows the journey of two heroes trying to conquer evil once and for all. It is a gripping fantasy adventure featuring Robert E. Howard's hero Cormac mac Art.