You basicly get a buff with +180 CR,+20 MD, and +5 Health regen for 1 minute, but by hitting mobs you have a chance to renew it, but it dosen't happen too often and your lucky if the buff last more than 2 minutes.
Path of the Enlightened will remove the curses in Kara Korum for the time it runs.
You can also use it in dungeons, which I find usefull as a tank to use it just before the fight starts to gain some extra hate on the boss. While using it your apperance also changes and you become a "Jiang Shi" for the duration of the buff.
It has a 10 minute cooldown once used.