The Preomnor, also called the Neutralizer, is the 7th of the 19 gene-seed organs that are implanted into a Space Marine Neophyte to produce a new Astartes. The Preomnor is essentially a second or pre-stomach spliced into the human digestive system above the original stomach that allows Space Marines to eat otherwise poisonous or completely indigestible materials. The Preomnor is capable of biochemically analyzing ingested materials and neutralizing most known biochemical and inorganic toxins, and many others that remain unknown save for their toxic effects. Deadly poisons are either neutralized or isolated from the digestive tract by the Preomnor. The Preomnor can also be isolated from the rest of the digestive tract to deal with particularly toxic substances that a Space Marine may simply vomit back up later. Often these extracted toxins are rerouted and then molecularly stored in the Betcher's Gland for future usage by the Astartes.
- Codex: Black Templars (4th Edition), pg. 10
- Codex: Space Marines (5th Edition), "The Making of a Space Marine," pg. 11
- Index Astartes I, "Rites of Initiation - The Creation of a Space Marine" by Rick Priestley & Gav Thorpe, pg. 3
- Warhammer 40,000: Compendium (2nd Edition), "The Origins of the Legiones Astartes" by Rick Priestley, pg. 8
- White Dwarf 98 (UK) (1988) "Chapter Approved: The Origins of the Legiones Astartes" by Rick Priestley, pg. 14