"They're biomechanical weapons. We had to come up with what would be the ultimate version that could actually, in principle, stop the X-Men. We started with this idea that they were almost made up of magnetic plates slapped over one another, imagining that the plates could contract or grow, so the Sentinel can be skinny to get through a small space or the plates can open up to become a bigger shape. So they have become virtually unstoppable."
Covers of the other characters found here & here
Kitty Pride/Ellen Page
LOL! The future covers looks so much better than the past XD