This skill allows you to regenerate faster by concentrating on your inner
evil. In order to fully reach the meditative state, you must sacrifice either
health, power or endurance, and thus you only get the benefits on the other
two. Those who are proficient enough in the skill can just concentrate on
malice to regain their standing with Draen-Dalar. Your alignment, wisdom and
proficiency in dark meditation affects the outcome, as well as your
environment to some degree. 
You can 'stop' to end the meditation.