Sensei

Sensei is a Japanese word which means "Someone's elder" and is often used as an honorific for teachers.

In the Warhammer 40,000 universe, the Sensei are supposedly the immortal offspring of the God-Emperor of Mankind, left over from the time when he was walking around and living as a man. In the good ole' days of the fluff, their end goal was to achieve apotheosis and merge their souls with the fragment of the Emperor floating around in the warp - the Star Child. They were also all blanks.