It's the posture that sets Magneto's teeth on edge, causing him to pull inward, power and energy coiled tightly around him like cable spooled so much onto itself that it's threatening to break. Around him the air thickens with ozone and heat, and even if his body is adapted to the oxidizing effects of it the other organic matter in the close vicinity will soon begin to suffer for it.

"As long as SERO was hunting me and the others." Magneto's own tone was calm, simple. Accepting of what was. He delays slightly, a few seconds, as he debates asking how Castiel knows he was pretending to be dead and not simply having just returned. "I'm not pretending to be dead, Castiel. I'm keeping my presence mostly hidden."