H. P. Blavatsky

Septerium. A great religious festival held in days of old every ninth year at Delphi, in honour of Helios, the Sun, or Apollo, to commemorate his triumph over darkness, or Python; Apollo‐Python being the same as Osiris‐Typhon in Egypt.

Source: H. P. Blavatsky, The Theosophical Glossary, art. Septerium