Hard To Be a Leader

From HammerWiki

Kill a Drakk Cultist in Thunder Mountain (17k, 5k or 15k, 2.5k) to unlock this. The Drakk Cultist that is sitting down with the group in the middle usually gives the unlock. Also gives credit to any member in the entire zone, as long as they are grouped in your group, not warband. This Drakk is only available once, if he dies you need to reset the Public Quest, but try killing all Drakk Cultists in the area if the first one does not provide the tome unlock. The Drakk Cultist behind a tent near 15k, 2.5k has been known to give the unlock.