Woad Warriors

Woad Warriors, also known as Berserkers, were various bizarre warrior cults during the time of Sigmar. Typically, Woad Warriors went into battle naked considering it shameful to wear armour of any kind. Instead, they painted swirling patterns onto their skin with a blue dye called woad. They covered their faces with ash, to give them a skull-like appearance. With these practices, they hoped to gain the protection of their war-god.

The night before a battle, Woad Warriors would dance around fires and walk through hot coals to prove their immunity to pain. The day of the battle, they imbibed an elixir of war, the ingredients of which have been lost in the mists of time, from an enemy's skull. They then danced around, bit their shields, and screamed and bellowed at each other. At the height of their frenzy, they charged headlong towards the enemy, bearing spiked shields, with no regard to pain, injury, or death. Many enemies fled merely at the sight of the crazed horde of naked fanatics charging towards them.

Some types of Woad Warriors include headthrowers, bladder hurlers, firebreathers, gutters, wailing harpies, and wildkin.

Source

 * The Empire at War
 * pg. 84