So if people with CHIM can freely change the dream at a whim, what is the extent of it, if there is one? If Septim was able to change the landscape of Cyrodiil from a jungle to what it is now is there anything stopping him from doing something like wiping out the Thalmor? Maybe making it so they never existed? Could CHIM have prevented Alduin from ever coming back? Is CHIM limited to just altering Mundus or can it also change Daedric and Outer Plains considering they are part of the dream as well?

This is the reason I don't like how so many people are CHIMsters. It seems like they'd have screwed stuff up more. Then again maybe because of the constant struggle to avoid Zero Sum, they have to plan their changes carefully.

Why hasn't Talos killed the Thalmor? If you didn't like the way your hand looked would you cut it off? I ARE ALL WE. The Thalmor are a part of the dream and thus a part of Talos.

Cause he mantled Lorkhan became the central earth bone(Something like it I assume).
He's now not in control but can actually be manipulated by mortals like the Thalmor.
Also being dead doesn't help.