Demons and monsters are connected to nature. They get their energy from nature, while humans also take that energy into their bodies to feed their souls to use as magic. The only difference between demons and monsters in this world was that demons could think while monsters lacked intelligence and were violent in nature. So it wasn't impossible that someone would try to use them to attack Lysanthia.
The moon was already high up in the sky, and her quarters were shrouded in darkness, with only the hearth providing her enough light to see something. Sera sat before the fireplace with an open book on her lap. The church was still trying to mess with her even after her banishment from the capital.