Allow me to second, or third or fourth/fifth Yahtzee's idea of losing power. (You people are ninja's.)
He noted that the problem is that the player needs to know about the area first, which makes sense. What if this... What if we were lead through the conventional level system, going through all of these areas, unlocking secrets, ETC. And then this big attack happens. The main area where your precious 7-11 is gets jumbled, and forces you to relearn that area. One by one, you have to go through each area, getting hit by the final boss to lose x ability. Until the very end, where the big bad boss goes after the 7-11. The hub area may have some new abilities to play with that you must unlock to save the day, but that's an option.
Eversion also has an idea that might play well with this. Perhaps in certain areas, you can see a glimpse of the monster's world, maybe go through a hidden "gate" to try and face his minions early on.
Something to keep in mind for your hobbies...