Tree-Gods and The Ring of Glass

So what was the ring of glass that Horn, Seawrack, and Babbie found on the herbal island? Light seemed to go one way through it, implying a dome meant to contain light, like a greenhouse. The original lab where the tree gods were developed? And what's under the ocean? Why does (Hoof? Hide? I forget) see a neighbor sitting on a tree limb coming from the ocean when he looks through a neighbor's ring? ...and why does Seawrack act startled at the mention of blood (possibly even the mention of biological characteristics through blood sharing) in Pajarocu? ...not connected, I know, but another detail I've always thought was a fairly large clue if I could just figure out what it means.

Good questions Brian. I am interested in how others will answer (and I must admit Marc's responses here are bit over my head). By mentioning "Tree gods" it seems a recognition that this ring has similar properties to the Sacred Windows on the Whorl which allow humans to view the gods of the Mainframe (and allow the gods to possess humans).

I think the remnants of the Neighbors' civilization, as the Commonwealth could be found under the oceans of Ushas.

I think Marc's answer has good significance and validity. I'd maybe want to add that Seawrack being started at the mention of Blood might be related to her spiritual connection to Hyacinth. The overwhelming lust found between Silk and Hyacinth is parallel to that between Horn and Seawrack, I think, (and Kypris and Typhon/Pas, of course). And we know about the relationship between Hyacinth and the character named Blood. So maybe it is related to that.