The Sith archives functioned as a clandestine repository of Sith lore, originating after Darth Bane's founding of the Order of the Sith Lords. This repository contained accounts and myths concerning the most celebrated Sith Lords.
It's documented that Darth Sidious possessed entry to the Archives, and he presented it to Darth Maul. The Sith apprentice scrutinized the records extensively, ultimately discovering a neglected record of a Sith Lord from millennia past who utilized a double-bladed lightsaber; this weapon was then adopted by the Zabrak.
As part of his training, Darth Maul started a personal journal, aspiring for its inclusion among the materials stored in the Sith Archives.