Lore: After holding out on Isstvan for months, Saul Tarvitz, along with other remaining loyalists of the traitors' attack, was finally killed in Horus’ final orbital bombardment of Choral City. However, this isn’t the full tail. In reality, Saul, while heavily wounded, survived alongside 200 Loyalist Emperor’s Children and managed to escape from the planet. Jumping into the Warp, they tried to make their way to Terra quickly and warn the Imperium of the Traitor's might. However, the journey took 3 months, worrying the survivors as they were forced to entomb Saul in a Contemptor dreadnought to keep him alive. They finally arrived at Terra, hoping to earn them before it was too late. But it was far worse than they imagined. Instead of traveling for 3 months, they’d been lost in the warp for almost 10,000 years. It was the 41st Millenia.

An Emperor's Children ship showing up at Terra without warning caused panic, and the vessel was fired upon. The marines believed that Holy Terra had been compromised. compromised tried to defend themselves. However, they would be spared when, ironically enough, an inquisitor hailed them and asked who they were. They explained their situation, including the fact that they had an injured Saul Tarvitz on board. The attack ended, and they were allowed to explain themselves fully.

Following the cease-fire, the marines were filled in with what happened over the past 10000 years and why they'd been fired upon. In dismay, they requested a planet to rebuild on in seclusion and were granted in, under close watch by Grey Knight operatives. A few hundred years later, the Eyes of Silence emerged.

Appalled by what became of Fulgrim and the Children, they have taken great strides to ensure Slaanesh can never claim them and have embraced the saying of "See no evil, hear no evil, say no evil" by using unique implants. First, they replace their tongues with an emitter, denying Chaos a sensory organ and allowing them to emit low-frequency infrasound and high-frequency pings. They then install sensors in their ears to pick up low=frequency infrasound and to deafen any other sound, denying Chaos another sense. Finally, they replace their eyes with unique audio sensors to pick high-frequency pings, allowing them to "see" this sound and again denying Slaanesh a sense.

Together, these create soldiers that echolocate to see and can communicate silently over two miles without radios. To go along with this, they can only "see" when they aren't speaking, further driving them to silence. To communicate with others, they have developed a form of sign language but rarely use it.

As weaponry, they use modified sonic canons that fire silent Infrasound that can disrupt bodily functions, vibrate through walls and vehicles and rupture heads behind cover.  This weaponry is devastating against the Orcs and Tyranids, disrupting the WAAGH to cause their tech to fail and erupting heads like a Weirdboy backlash and even causing panic and confusion amidst the Tyranid Hivemind. However, these weapons are useless against the daemons of chaos except, fittingly enough, Noise Marines. The "silent sound" is the only kind of audio pain that bothers them and causes immense distress and pain before killing them violently. The weaponry also has almost no effect on Necrons and the Eldar, though Dark Eldar are extremely susceptible due to no longer using psychic powers.

Their vehicles are likewise silenced, using stealth versions of typical vehicles. Most uniquely, they make use of "Pulse Raiders", modified stealth land raiders that sport a much more powerful version of the infrasound cannon as a weapon. Unagumented "Stealth Marines" act as pilots for the Eyes of Silence and help integrate them with others. However, unsurprisingly, not many other Chapters like working with them, being unnerved both by their augmentations as well as the almost completely "silent" combat doctrine. Despite this, the Eyes of Silence bravely fight on, desperately hoping to never fall to Slaanesh's whims or betray the Imperium ever again.

Their chapter master is a reborn Saul Tarvitz, who now lies entombed within a specially made Dreadnaught. Renaming himself Humiius Si to draw less attention to himself, he leads his new Chapter against the enemies of the Emperor, acting as both leader and the main diplomatic figurehead to the other Space Marine chapters and forces of the Imperium. It was he who oversaw the creation of the Sonic rifle and the development of the sign language that the Eyes use when communicating with other Legions.

The Eyes of Silence (Custom Loyalist Marine chapter)