Wurrzag

Wurrzag Ud Ura Zahubu, also known as Da Great Green Prophet is a Savage Orc Shaman of mighty mystical powers. Wurrzag leads tribes to greatness before wandering off to pursue yet another mad plan to advance Orcish kind. Like all Orc Shamans Wurrzag is completely crazy, though what he lacks in sanity he more than makes up for with vision and inspiration. It is widely believed that an army with Wurrzag in it has never been defeated in battle.

It's not unusual for a wizard to be a bit odd, but Wurrzag is a complete raving lunatic. While most wizards are quite happy to stay out of harm's way and cast spells from a distance, you will find that Wurrzag is most useful in the thick of the action, dancing around and blasting green bolts of energy from his eyes. Even more worryingly, wizards tend to degenerate into rabid squiggly beasts when Wurrzag gets close, prompting a mass magical exodus from his general vicinity.

Source

 * Games Workshop webpage