Forerunner capital survives halo

"The Lifeworkers have sworn to carry out the commands of the New Council, reconstituted from survivors found deep beneath the ruins of the Capital world. Most of the Old Council was killed by the metarch- level ancilla known as Mendicant Bias when it unleashed the killing power of Halo, possibly at the instigation of the Master Builder."
(Halo:Silentium; Ch.2)