The half-Earthling, half witch-brood descendants of Simon Tregarth: Kyllan the warrior, Kaththea the untried witch, Kemoc, whose powers could surpass all others - face the sorceries of an unknown enemy. The burden of the struggle falls to Kemoc, who is forced to summon his untested powers in the battle to match the alien evil threatening the Witch World.
Andre Alice Norton (1912-2005) was an American science fiction and fantasy author (with some works of historical fiction and contemporary fiction) under the noms de plume Andre Norton, Andrew North and Allen Weston. Norton published her first novel in 1934, and was the first woman to receive the Gandalf Grand Master Award from the World Science Fiction Society in 1977, and won the Damon Knight Memorial Grand Master Award from the Science Fiction and Fantasy Writers of America (SFWA) association in 1983.
Andre Norton. Wikipedia.