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Originally Posted by SceleriS  Stark has a failing Heart ..the suit helps to keep him alive. Tony Stark cannot live without his suit for too long or he'll die. |
Yeah, there's a piece of shrapnel near his heart. When he was captured he designed a device that would use a magnet to keep the shrapnel held in place so that it wouldn't get any closer to his heart and kill him. The glowing ring is that device.