Trillium, or World of the Three Moons
Black Trillium – 1990 (written by Andre Norton, Marion Zimmer Bradley and Julian May
Blood Trillium – 1993 (written by Julian May)
Golden Trillium – 1993 (written by Andre Norton)
Lady of the Trillium – 1995 (written by Marion Zimmer Bradley)
Sky Trillium – 1997 (written by Julian May)