Wow.
I normally don't enjoy horror movies, but this was simply amazing. The story made sense, the art was well drawn, and it certainly managed to scare me. This 'Sacred Tree' instilled a lot of man's natural fear of what he can't see.
What would've made it better is maybe a little more at the end. Possibly having the (SPOILER ALERT) possessed main character continue a conversation with the friend. Now that would've been freaky - seeing what terrible things this thing would write.