Librarian

The Librarian was a Forerunner being.

He/she sought to document and index all sentient beings of the Milky Way galaxy and protect them from the Flood by sending them to the shelter of the Ark He/she was left on what is more likely Earth soon before the original activation of the Halos, unable to leave the planet due because of the severity of the Flood/Forerunner war.

His/her lover was the Didact, believed commander of the Forerunner military.