From Halopedia, the Halo wiki
The Charybdis system was a UNSC-controlled planetary system home to at least nine orbiting planets, including the human Outer Colony world of Charybdis IX. In 2535, the Covenant invaded and glassed the planet in the Battle of Charybdis IX. Several days later, the Prophet of Regret remained in the system, aboard his personal cruiser. He was visited by the Prophet of Truth, and eventually the two departed from the system.
The system was likely named after Charybdis, the daughter of the god Poseidon in Greek mythology. She was a nymph that was turned into a sea monster resembling a gigantic whirlpool by Zeus. Charybdis' companion sea monster was Scylla.
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