The user of said ability can use a completely random power at will. However, they have absolutely no choice of what power they receive. It could range from the ability to fly, to shape-shift, etc. The power that has been received can only be used once. However, though there is a very small chance of getting the same power twice, it is completely possible. Mutations that can be caused by this power are only temporary, and will vanish when a new random power is received.