Before attending any raid listed below DON'T FORGET to return to Grandfather Takk in Graystone Yard (3/30/2014 With the Qeynos revamp, NPC now in Eldarr Grove Loc (702, -17, -336)
to pick up the next portion of the quest (for the mythical version of the weapon), which requires you to retrieve three fetishes to fully unlock the powers of the cudgel. These all drop from raid targets and can be done in any order.
The first is the Fetish of Spirituality, which drops from Pawbuster in The Execution Throne Room.
The Second is the Fetish of Preservation, which drops from Venril Sathir in his lair.
The Third is the Fetish of Enlightenment, which drops from Hoshkar in Veeshan's Peak.
After you have obtained all three fetishes, return to Takk to receive your mythical.