Time of the Twins1986
(Test of the Twins)
by Margaret Weis
Raistlin casts the magical spell that has cost him so much. For him, the Portal opens…
But, at the same instant, his twin brother, Caramon, operates the magical time-traveling device. The fields of magic shift and collide.
Caramon and the kender, Tasslehoff, are flung into an unexpected time and place where they make a horrifying discovery.
And Raistlin enters the Abyss, prepared to face his most deadly challenge -
Takhisis, Queen of Darkness.
— from OpenLibrary
37 editions at OpenLibrary