The power of maya is known only by its effect, the world. Further the power of maya is actually the power of brahman. And although maya is the power of brahman, make no mistake, maya isn't brahman.
Whereas maya is not absolute existence, neither is maya non-existent. Relatively existent, maya is as it is, undefinable and indescribable.
Before creation, there was maya, the darkness of maya covering the light of brahman. Brahman adorned in the cloak of maya is isvara, god, the saguna brahman, or the absolute with attributes.
And the first transformation of maya is space, in which the world appears, for brahman is spaceless, space being just a superimposition on the substratum of brahman.