Jill's got her work cut out for her. While her draconic steed affords her excellent mobility, and Jill herself is considerably less frail against magical assault than the typical Wyvern Lord, Venusaur's status assault is still deadly accurate. Fortunately, he's no faster than Jill, and his offense is less than stellar, meaning that Jill can afford to spend a few rounds napping. Her trusty axe will quickly cut through Venusaur's leafy hide, and while the plant-dinosaur... uh, thing will probably get a Sleep Powder or two in, Jill will dodge her share as well, giving the machette-like assault time to trim the vines and give Jill a well earned win.
