The Forbidden Tower is a science fantasy novel by American writer Marion Zimmer Bradley, part of her Darkover series.

[2][3] The Hilary Castamir stories in the collection Marion Zimmer Bradley's Darkover precede the events in The Forbidden Tower by about ten years.

Leonie tells him that she wishes to persuade Callista Lanart to return to Arilinn Tower and replace her as Keeper.

She is aware that Callista wishes to marry the Terran, Andrew Carr, who rescued her from the Caves of Corresanti (as seen in The Spell Sword).

The next day, a joint wedding is held – Ellemir is joined to Damon and Callista to Andrew in freemate marriage.

Andrew recalls that Leonie has warned him that Callista was trained in the old ways of Keepers, and may not be able to consummate their relationship for a long time.

Desiderio Leynier, a nedestro relation (Dom Alton's illegitimate son), creates trouble at the wedding feast.

When it becomes clear that some of the men will lose their feet to frostbite, Damon, working with Andrew and Dezi, uses his laran powers to restore their circulation.

Varzil recommends the sacrament of Year's End as a way of freeing Callista from her Keeper's restrictions, but the meaning of the ritual has been lost.

Damon breaks down the remaining emotional walls separating the two couples, realizing that essence of the sacrament of Year's End is a shared sexual experience under the influence of kireseth flowers.

Like the Darkover-Renunciate books, what underlies The Forbidden Tower is a discussion of the value of monogamy, women's roles in society, the place of one's family in decision making, and whether a woman may act as an agent independent of these forces.