From Warhammer 40k - Lexicanum
The Ordo Katastrophica was a secretive Mechanicum organization during the Great Crusade and Horus Heresy.
A highly independent order, it consisted of Magi agents of change who promulgated a scientific philosophy of discovery and innovation at odds with the Treaty of Olympus.
- 1: The Horus Heresy: Age of Darkness Rulebook, pg. 123