Ordo ad Chao is the fourth full-length album by the Norwegian black metal band Mayhem. "Ordo ad chao" is incorrect Latin (correct: "ordo ad chaos") for "order to chaos" – a reversal of the Latin expression "ordo ab chao" ("order from chaos") often cited as the motto used in Freemasonry. It is the first Mayhem album with the vocalist Attila Csihar since the 1994 album De Mysteriis Dom Sathanas and the last with Blasphemer before he announced his departure from the band in 2008. As paert of the "new" life of Mayhem this record draws back to the origins of the band while incorporating the visionary approach of the a band that never stopped evolving.