Zeratul is one of the central characters in the StarCraft series. At six hundred and thirty-four years old and holding the rank of prelate, Zeratul is a member of the Nerazim, better known as the dark templar, whose forebears were exiled from the protoss homeworld of Aiur over a thousand years ago for refusing to submit to the Khala. A renowned psionic warrior and assassin, he is described as a "savior" and "willing scapegoat" for his people. During the later episodes he takes part in defeating the Overmind on Aiur and reuniting the dark templar with the rest of their people.
Source: Wikipedia, "Zeratul", available under the CC-BY-SA License.