A warhammer is a heavy hammer, and can be wielded with one or two hands. It is a Military class weapon. The warhammer deals 1d8 bludgeoning damage plus strength for normal attacks, and x3 damage when you Critical Hit something.
Warhammers are available in different materials, as well. The useful versions of the warhammer are available in steel, orwood, and Wysharna’s Bark. The orwood version is a druid-only weapon, as is Wysharna’s Bark.