From Halopedia, the Halo wiki
Celebrator-of-Birth was a first-form Lifeworker.
During the evacuation of Erde-Tyrene, Carrier-of-Immunity, the chief Lifeworker on the planet, received a signal from his seeker transport, informing him that the Librarian was in the system. Excited, Celebrator-of-Birth asked if they were going to meet the legendary Lifeshaper in person. Carrier replied they would not, as the planet's largest human city of Marontik had not yet been processed.