The Warhammer Online Herald has been updated with a new 'In Development' article. The article is entitled "Play as Skaven" and features the lore behind the Skaven and outlines the various playable classes of Skaven: Warlock Engineer, Gutter Runner, Rat Ogre, and the Packmaster.
The Packmaster supports a Rat Ogre as best he can. By just being nearby, the Packmaster’s influence increases the effectiveness of his Rat Ogre. The Packmater’s attacks can be used on both enemy and ally, having different effects on both. Being skilled and powerful leaders and organizers, the Packmaster is able to exert his influence to nearby allies for a short time, helping to increase their effectiveness as well. It’s that same power of pack manipulation that also allows the Packmaster to summon forth rat minions for short bursts of combat.
Read the very comprehensive look at The Skaven here.