It wasn't as though Magnus felt particularly good about killing the creature (presumably), though he wasn't exactly remorseful, either. What he was, was annoyed as Hammer began to speak and then- much to Magnus' chagrin- touched him. When the other man's blathering was finished, Magneto turned to him with a cold eye and a cool warning, "Touch me again and lose your hand." Simple enough and the absolute truth.
Threats aside, there was something far more important at hand and Magnus shrugged away from Justin to walk to the space where the dragon had just been and stare up at the top of their domed prison. There was something there, very small, a contraption to relay the teleport no doubt and maybe their chance at freedom. Magnus doubted very much that winning that match meant their gracious host would simply let them go. Likely, there was to be some new and worse horror to follow the dragon.
Turning abruptly and staring at Justin with the disgust one generally reserved for a particularly foul insect, Magneto addressed him with the question, "If I got you up there-" He jerked his head towards the dome, "Could you adjust the teleporter to get us out?" It would be a miracle, certainly, but maybe Hammer could prove useful after all.