A sentient patch of trees and land on the outskirts of the Whateley Academy campus. The Grove is an ancient entity that's withdrawn into itself because of the mess that humans have made of its world. It maintains a field or spell that subtly redirects people away from it.
There are a small number of humans that it tolerates because of their connection with nature or for other reasons. It absolutely dotes on Nikki Reilly because it recognizes her as The Daughter of the Burning Oak, the Queen of the West. Nikki finds this a bit disconcerting. It recognizes Tennyo as the Star Stalker and considers her a danger to Fey. It would much rather have nothing to do with her, but tolerates her because it knows how powerful she is. It likes Razorback, Chaka and The Handmaid of the Tao. It tolerates Jericho because he's associated with Razorback and instrumental in the fight against the Voodoo Wolves.
Charlie Lodgeman goes into the Grove to meditate, and Tennyo follows. It almost kills one of the security guards who tries to penetrate it. The following day Tennyo leads Nikki there, much to the joy of The Grove; well, joy about Nikki, it'd just as soon not see Tennyo again.
It's heavily involved with the fight against the Voodoo Weres.