When "X-Men: Days of Future Past" comes out this weekend, the X-Men will take on mutant-hunting robots known as the Sentinels.

For the film's production designer John Myhre it was important to bring the killer machines to life while also focusing on their look from the comics.

"The first thing I did was say, 'What do the Sentinels look like?' And it’s amazing how often they’ve changed since the 60s and stayed quite often the same," Myhre told Collider.

For example, when the Sentinels first appeared in X-Men No. 14 back in 1965 they looked more human than robot.

As the years went on, they became more and more robotic looking while varying in detail and size.

Yet, they maintained their signature look focusing on their purple helmet shape and glowing yellow eyes.

For "X-Men: Days of Future Past" Myhre created two different versions of the Sentinels to match the two timelines of the film.

The premise of the movie will see Hugh Jackman's Wolverine character getting sent back in time to prevent the creation of the giant bots.

The 1970s version of the machines stayed true to the robots' look in the comics.

Myhre went in a different direction for the futuristic version of the Sentinels, coming up with an entirely new design.

If you've seen the film, you know this is because *minor spoilers* the future Sentinels are made with the help of the shape-shifting mutant Mystique's DNA. *minor spoilers*

"They're biomechanical weapons," Myhre told Empire. "We had to come up with what would be the ultimate version that could actually, in principle, stop the X-Men."

To do this Myhre reconsidered both the design of the robots and their ability to attack mutants.

"We started with this idea that they were almost made up of magnetic plates slapped over one another," Myhre added. "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."

This includes shape-shifting parts of their bodies into weapons.

While also being able to change in size to take on the strongest X-Men.

By doing this, Myhre took the iconic design of the Sentinels and made them an invincible force in the film.

"They have become virtually unstoppable," Myhre said.

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