Curses come in many forms. It can be a personal plight someone sees as a curse or a powerful hex bestowed by a witch. The latter curses are used to turn enemies into frogs. Frogs, toads and slaads are all familiar to the frog god itself. Burglefloogah sees all of them as its own kin. While many servants of darkness might welcome transformation into the form of their god, they're also familiar with the process of transformation and are able to protect against it.