Condition exclusively caused by Chryseis' 3rd skill on Rotation "Charm" which is used on the Frontmost hero. A form of Disable or Crowd Control, being charmed causes a hero to lose control and start attacking an allied hero closest to him or her. While charmed the hero may use skills on rotation. Charm interrupts most skills that are being used, however, depending on the the timing, some Ultimate skills can damage the charmed hero's team (Hecate and Achilles). The charmed Hero can still be healed and buffed by their allied team.
NB: Hades' ultimate Death's Veil and Aphrodite's Loving Embrace negate Charm. Magic immune creatures are unaffected.
An example of how charm can turn the tides of a battle; whether in Arena, Gauntlet, or etc.:
Achilles Charmed 12-20-14-07-58