Terrigen. Antigen. Amphogen. All imperfect attempts to re-create the pure catalyst. The first catalyst. Primagen. The prima materia...that created the Kree. 
Primagen is a potent mutagen used by the Progenitors. All Inhuman catalysts are failed imitations of it.[1]
History
The Primagen (also known as Prima Materia) is a substance created and harvested by the Progenitors in the Garden-World inside the World Farm used as fuel. To the Progenitors, Primagen is easily farmed and widely used.[3] The Primagen was additionally employed as a catalyst to evolve the Kree from their primitive form.[2] The Kree's failed attempts at re-creating it resulted in the much less pure Terrigen, Antigen, Amphogen, and others catalysts.[1] To the Kree, the Primagen became a forbidden legend, of which only high-ranking Kree soldiers have the clearance to discuss it.[4]
Harvesting process