Reply-Code Omega is a signal that Algalon the Observer could send to the Titans, signaling planetary re-origination. According to the Archivum Console of Ulduar, Reply-Code Omega is one of two possible reply signals following by planetary diagnostics after the arrival of Algalon.
"Planetary re-origination" would result in the destruction of modern Azeroth and its reconstruction from the raw materials, recreating Azeroth from the original Titan blueprint. The re-origination device itself is located in the Uldum desert. Given the death of Prime Designate Loken, the corruption of the Titanic watchers, the destruction of the Well of Eternity, the corruption of one Dragon aspect and the death of another, and the release of the Old God Yogg-Saron, the chance of Algalon sending such a signal is estimated around "99.99%, repeating of course".
- Reply-Code Alpha: signaling all is well