Y'know, I just realised. Great tree, demons.. I think this is based on the mythology of Life Trees. Many different cultures have them, and different stories, as well as different species of life tree.. Oak, acacia, fig.. But many of those stories involve some sort of evil the tree protects against. Be it malevolent spirits, the monsters in the dark, or even real creatures, like wolves or other large predators. I love the idea that this whole thing could be beautifully rooted in some ancient mythology, telling its own version of such a tale.