Which is apparently a thing they can do, what the fuck.
Its not a very popular thing among marines to do, aye.
And then the vast majority proceeded to go "Nah, not gonna do that." Emps must have been banging his head into a wall when he found out his super soldiers are flat out refusing to use one of the organs he spent so much time developing.
Yeah, a lot of Legions didn't really make use of the Omophagea to its full potential.
Right up there with acid saliva on "whatthefockwereyahsmokin', Emps?"
The Acidic Saliva combines with their Omophagea and ability to subsist of rocks to actually give them the ability to melt those things and make them digestible.
The Revenant Legion was special in their use of the Omophagea for also having newer marines eat their own dead veterans to rapidly train them, IIRC?
God damn I love the Revenant Legion.
Just the coolest showcase of 'To Fight monsters we created our own'. Not to mention they have the highest growth rate of the Legions (What with the 'fill them with Juice, toss them in a coffin and bake for a year'), would regularly engage in cannibalism to turn raw recruits into veterans and the pseudo-immortality of their officers.
Really, what more could you want from a Legion? I'm not saying that Hawk-boy ruined them, but he made them a lot less cool.
The Revenant Legion were the Space Marine legion that fully leaned in on all the monstrous aspects of Space Marine biology. Their geneseed could recruit the most horrifically mutated of humans and make them into marines. They actively used their Acid Glands due to them eating the hardest and least digestible mutant and alien brains around.
And most importantly. They AGGRESSIVELY used their Omophagea to its full potential.
After every battle, they'd eat the brains of every remotely useful enemy to gain additional knowledge.
If one of their members died, they'd keep the body for a cannibalistic post-battle feast where all the knowledge they had would spread.
New recruits would eat the brains of experienced members to immediately give them the training and skills of said experienced members
And officers would have one marine ve chosen to eat the entire damn body so they'd absorb all their knowledge and become said officer, and with some corrective surgery and hypno-treatments, pretty much become the one they ate.
So not only could they recruit from damn near anything human, (Amit the Flesh tearer was closer to a mass of angry tentacles than a human) each of their members who died would help multiple recruits to quickly gain skills and knowledge, spread additional knowledge throughout the ranks of the Legion, and they had a near-immortal officer corps that carried on institutional knowledge that grew with each new officer who took on the persona of said officer.
There is a scene in a Horus Heresy campaign book where a band of Terran Blood Angels apparently went a bit mad due to the Heresy and collapsed back into their Revenant Legion days.
They were aggressively growing in strength through the Heresy due to all their omeophagic habbits, recruiting from damn near anything viable, eating traitors and their own dead in order to rapidly train and improve these new recruits. Officially they were tagged as Inductii, but these new recruits were all as good if not better than the average marine due to accumulated knowledge.
During the Battle of Beta Garmon, they countercharged the World Eaters and matched them in brutality to the point that the Imperial Fists banished them from the fortress. A few hundred of these Blood Angels went to ground in a part of the hive after their praetor died. Traitors and loyalists alike avoided them due to their propensity to kill first and eat later.
A few months after, when the city had fallen the traitors were about to leave.
And a thousand blood angels in scavenged and stolen armour without repainting any of it, charge out of the ruins, with all of them being skilled fighters thanks to all the dead veterans around them.
And it turns out they were doing accelerated marine recruitment in a few months,
using scavenged underhive medical equipment to make Inductii and feeding the recruits the enemy veterans to make them better at combat, putting their praetor in a damn dreadnought. They charged out of the city, butchering their way through the traitor forces carrying off their loot, freeing their slaves, killing the traitor auxilia defending their dropships, and flying off into space to find another battlefield. And although less numerous, they had certainly gotten deadlier in terms of all the accumulated fighting experience.
The Revenant Legion were the Space Marines without all the niceties: A self-replicating genetic superweapon that became smarter and deadlier as it killed, could survive off anything, and would recruit nearly anything human.