Dryad

They’re a type of elemental that dwell in trees, and they’re called “Demi-Elementals” since they were originally born as monsters. They nestle close to a single tree for their entire lives, and when the tree dries up, their lives end, but the trees they dwell in can keep living for thousands of years by continuing to suck spirit energy from men. Due to their rich demonic energy, they can protect themselves from searing flames and bad diseases that infect trees. They’re normally warm, but they will attack those who threaten the forest without mercy with vines that pop out of the ground.