When the original witches had sent the curse in motion, they had created a malignant intelligence. Generally, it simply oversaw the carrying out of transforms and dares while delighting in the suffering it caused. But as the curse became used more and more in different ways, the curse grew more powerful but also more self-aware.
And it wasn't happy.
Its goal was to cause suffering, and its users didn't seem to be respecting that. On the contrary, even though the curse could admire the evil of what it had done to Martha and the shadows particularly, they weren't miserable. The best curses were done in hatred and resentment, as Kyle and Jennifer's original curses had been. The agony of original Kyle, as he had lost his personality to be made into what he most despised--a female--that had been something to savor. But making people into happy little she-wolves? What was the point?
The curse was bound by certain rules, but ordinarily it knew these rules better than the users. These users seemed more careful and aware than users were normally. The curse's first attempt to break the circle of its current users, Zack, had been caught before it be effective.
And there was another fear. If the users were actually serious about this taking over the world nonsense, they would invite the intervention of far more powerful supernatural beings, beings capable of ending the curse's existence entirely. The curse still remembered the pain and fear it had felt when magic had been used to end its existence in two victims.
The curse determined to use any kind of strained interpretation, to take advantage of any hesitation, to do anything to break the current circle of users and free itself.