simmer - To heat a liquid, usually a stew or soup, just below the boiling point, allowing it to cook slowly; or to stay in a slow, controlled state of progress or tension, often before a larger event or change occurs.

He was simmering with anger, but he kept it inside and didn't say out loud what he was thinking and feeling.
aura - The distinctive atmosphere or quality that seems to surround and be generated by a person, thing, or place.

She was immediately attracted to the aura of light and peace that seemed to emanate from him, though she realized this required validation and investigation.