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. The Librarian cut him/herself off from the Flood/Forerunner conflict by deactivating the portal leading to Instillation 00 (The Ark), leaving him/her isolated on Earth.

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