1. Compassion or forbearance shown especially to an offender or to one subject to one’s power.
  2. Lenient or compassionate treatment.
  3. A blessing that is an act of divine favor or compassion.
  4. A fortunate circumstance.
  5. Compassionate treatment of those in distress.

Phrase “at the mercy of” meaning “wholly in the power of, with no way to protect oneself against.”

The emotion of Merciful is found in the Large Intestine meridian in the Metal element.

Definition from Dictionary by Merriam-Webster.