I like the invention of rainforests with "shallow soul"
Yes, I know what you meant.
As for the Flying Buttresses, why not a stone column, kind of like Ansom's flying carpet only solid? I can imagine troops riding them like extremely thick witches' brooms.
Unfortunately, I've had way too much experience dealing with shallow souls, but never in a rainforest.
Anyway, Ansom's carpet is a magic item, so it can't be croaked. In Episode 20, it specifically refered to the Buttresses as units and to them being croaked. Of course, that doesn't mean they can't look
like Ansom's carpet, but they don't function the same way.