The Valley of the Tauran Bears is the 27th Proposed Serial in Spectral Shadows. It is preceded by Serial 26 - Return to Pentalous and succeeded by Serial 28 - Rosebud. It is currently not being worked on, meaning that the only available material is the summary on the Synopsis Page.
The summary is as follows:
Jon returns Rocinantè to The Dream Weaver feeling like a bumbling fool, utterly unworthy of the faith she had placed in him. But she informs him that he was the perfect instrument of her plans, and that he is now the captain of The Rocinantè.
Jon confesses that he does not share her confidence in his readiness to be a Time Captain. So The Dream Weaver offers him a little training mission to cut his teeth on.
She sends him to the planet Taurus 5, explaining that the planet has been completely written off in her book as irredeemable and doomed to destruction. Therefore, Jon has nothing to lose if he fails to do any good there. But if he can manage to plant some seeds there that might grow in the future and give the planet some value, she might decide to give it a new destiny.
Jon and his companion, Sonny, arrive on Taurus 5, transformed by Rocinantè into the form of the anthropomorphic bears that live there. But they find that there is also a population of elves, and another of anthropomorphic cat people that live on the planet - each of these three populations being, not at war, but seriously at odds with each other.
The Valley that The Tauran Bears live in has sheer glass walls. They can't get out, and nothing from above can get in. At first Jon thinks this is a defensive measure, but eventually he learns that the valley is a prison or pen, and that the bears are fed upon by a fourth tribe of anthropomorphic vampire bats.