Welcome to the Butt Train. I made a nice little vanilla pic for the Tumblr Butt Train...but I just had to gorify it a bit. So here is that: http://imgur.com/a/xMFfb

Gave it a story too:
As Mirage moved through the Corpus ship taking out several Corpus Engineers, she heard a small beep near her. Turning to look around she noticed a small Corpus maintenance bot rolling up behind her. As she began look at it she noticed its camera fixated on her ass. Whoever was behind that camera had good taste.

Just too amuse herself she lowered her shields and reached around behind her, sliding her fingers over her ass cheek, stretching and squishing it in her skin tight frame. She chuckled as she thought that someone on the ship was probably jerking himself silly. Unfortunately that was her last thought.

Before she even had time to notice a Corpus MOA had entered the room. It instantly fired a high powered energy blast, vaporizing most of her entire upper torso. Her severed hand clunked to the floor twitching about.

The MOA's engineer escortee entered and saw the Warframe's smoking lower torso still standing, her leg muscles locked in place as her smoking entines twitched and shuddered. He moved closer and saw the maintenance drone behind her. He knew one of his comrades was watching so he threw up the ancient sign for "Nice Job", just as Mirage's burning hot bowels emptied themselves into the frames remaining lower half. The stench and gas was so much that not even the suit could stop it from escaping. With one last jerking release the frame's legs gave out and it collapsed to the floor. The engineer grabbed her still twitching foot and drug her back to his team to show them the kill.

An hour later the section team had stripped Mirage's shit and piss covered lower half of what was left of her frame and had it delivered to the higher ups. As for her remains, the section commander had her cleaned and dipped in preserving fluids. These fluids made organic material as durable and long lasting as silicone. This helped to keep Mirage's lower body smooth, fresh, and self lubicrated.

After the process was done the her Lotus tatto was stamped over by the official corpus seal of ownerhisp. The commander took her body and put it on one of display cases in his dressing room. When his shift was over, he'd be enjoying a long night with her juicy ass.