Yesterday, Empire Magazine released 25 covers for their new issues, and each cover featured a different character from X-Men: Days of Future Past.  The series began with a Sentinel Mark 1 from 1973 and ended with drastically different version of the mutant-hunting robot in the future.  The 1973 version resembles the design from the comics, but production designer John Myhre explained the thinking of how they decided to take the robot to its final version.  Myhre says that the Sentinels become "biomechanical weapons" because, ultimately, the design would need to evolve in order to stop the X-Men.  The team started from the idea that these sentinels would be made from "magnetic plates" that can shift and change size, "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."  I think there's one character who might not have an issue with magnetic plates.  His name escapes me at the moment.

Hit the jump for the full quote and to see a full image of the final Sentinel.  To check out the Empire covers, click on the corresponding links for Part 1, Part 2, Part 3, Part 4, and Part 5.  X-Men: Days of Future Past opens in 3D on May 23rd.

Here's Myhre's full quote to Empire:

"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."