I saw this video and thought, "Jacob would so hit that. Hard" [link]
That is the queen of demons, Rangda, from Bali.
And I came to the conclusion that Jacob is a yaksha, which is a form of Hindu nature spirit that can be both evil and romantic, depending on it's mood. They are even formed in the roots of trees, so that classification fitted Jacob perfectly.
Don't worry about Nini. The only thing about this that'll upset her is that Jacob got lost on his way to the grocery store.