Zerthimon

Zerthimon was a gith who fought in the wars for his people's liberation from enslavement by the mind flayers. After philosophical disagreements with the insurgence leader Gith over the fate of the liberated people, he became a prophet and a leader of the splinter group who would call themselves githzerai, as they split from their cousins who had chosen to follow Gith, the githyanki.

Rumors & Legends
Githzerai legends told that Zerthimon was in a state of eternal meditation within a realm of spirits, from where he regularly sent visions to guide his people. They also prophesied the return of Zerthimon in the form of a powerful guiding spirit.