They came from?

The world was ended by mysterious monsters called eleven. They came out weird gate ways and destroyed human society. Katrina obtained a strange power in the panic and it is of that power that she survived.

One year later:
She finds someone else who survived, Maxwell aka Max, who in his eyes sees her as humanities last hope of surviving this further.

Where does these portals come from?
AND
Does Katrina has what it takes to save humanity or is she to selfish?

Why don't you find out for your self!