Shamanistic might be an option, it uses Wil+Cha for its drain attribute which could be beneficial since the number of bound spirits is limited by Cha. Maybe cast detection spells and find any nearby animals, have a bunch of low-level bound spirits possess them and use their innate Control Animals power to take over a huge group. It'd be pretty freaky to get attacked by a huge group of amped-up devil rats or something.