From publisher blurb:
The shatterskull adept is a master of simple, heavy bludgeoning weapons, primarily the heavy mace and morningstar. He is an unsubtle and uncompromising warrior, and can deliver truly "bone-shattering" strikes with his chosen weapon. Like all Master at Arms classes, the shatterskull adept is a straightforward, 5-level prestige class for fighters looking to take weapon specialization to the next level. So give your fighter a reason to bust some heads with Blackdirge Publishing and the shatterskull adept.
Master at Arms - Shatterskull Adept contains 6 pages of new d20 material and features the following:
The 5 level shatterskull adept prestige class
Historical perspective on the heavy mace and morningstar
Author's design notes
Edrek Orcsunder, an iconic shatterskull adept NPC