The Seraphim are an alien species introduced in Supreme Commander: Forged Alliance as a playable faction. It is the species that the Aeon found on Seraphim II, and who taught them about The Way. Humanity thought it destroyed the race, but actually the colony on Seraphim II was comprised of exiles who believed they could follow The Way without sacrificing the ability to fight.
When the Black Sun was deployed, it created a rift between the Seraphim realm and humanity's realm. An army of the Seraphim came through the rift to cleanse the galaxy.
Seraphim Warriors
Because of their close connection to The Way, and the extreme empathic feelings that arise from that connection, the Seraphim are physically incapable of harming another sentient being. In order to wage war, the Seraphim utilize warriors that have agreed to permanently sever their connection to The Way.
The results of this action are immediate and extreme. Once a Seraphim loses its connection to The Way, they transform into emotionless killing machines. But becoming a warrior exacts a much heavier price than the simple loss of emotion. Since Seraphim society is built around "feeling" each other empathetically, Seraphim warriors are no longer able to associate with the rest of Seraphim society. From that moment on, they are outcasts.
In addition, Seraphim religious beliefs hold that only one species can ascend and attain perfection via The Way; therefore, any Seraphim that severs its connection to The Way is agreeing to forever relinquish any chance of eternal bliss. In effect, they are "damning" themselves for all eternity.
Seraphim warriors are managed by specially trained War Leaders that create a battle's overall strategy and then use The Way to keep Seraphim warriors calm and focused during battle. The latter is especially important because a Seraphim warrior can easily slip into a killing frenzy and inadvertently alter a carefully constructed battle plan.
Seth-Iavow is the War Leader of the Seraphim warriors who invaded humanity's dimension.
Doctrine
Units: Seraphim Units
The Seraphim units are composed of some superior technologies and sleek designs, somewhat resembling the Aeon. Their units appear organic in design, like the Aeon, but possibly more alien and foreign, such as their T3 mobile artillery appearing to have an eye on its design. They are very much multi-purpose units. For example, the Combat scout is a scout with stealth and cloaking fields when stationary, but also a light assault bot. The Seraphim experimental units are the Ythotha/Othuy assault bot, Yolona Oss strategic missile launcher and Ahwassa strategic bomber, their experimentals are extremely powerful but are very limited to what they are meant to be doing on the battlefield, with this considered the other three factions have found considerable ways to rival, and in some areas outmatch the technological advantage of the Seraphim.
Seraphim construction bespeaks a race far beyond the UEF, Cybran, and Aeon. The majority of Seraphim structures appear highly delicate, implying materials many times stronger than the alloys that compose most of the Human Forces. They make widespread use of hover technology, implying a home world with lower gravity. This is also confirmed in many of their units. The Seraphim ACU possesses thin legs and is very top heavy, with much unaccounted for space. The Experimental Assault Bot, the Ythotha, has a lope that covers ground at an alarming rate. Their unit designs are marked by asymmetry and curved, flowing surfaces decorated with some sort of crop-circle like engraving on the surfaces. Quite a few of their structures are supported by pillars of light, or possess components that are completely unsupported, seeming to float in the air. In fact, their entire Air Factory floats in thin air. Most of their weapons are marked by some sort of glowing orb attached to them.
Experimentals
"Ythotha" Experimental Assault Bot: Very few humans or cyborgs have seen this deadly unit and made it out alive. This assault bot is one of the best all-around units, and maybe better than other factions' counterparts. With 3 main direct-fire weapon types and the ability to outrun all other ground experimental weapons the Ythotha is effective against most land units and considerably effective against structures or base defenses. Making it one of the deadliest options for a land assault. Beyond assault, the Ythotha can defend itself from small amounts of aircraft as well as when destroyed it will release an unstable quantum energy that uncontrollably attacks everything around it, including allied units. It does have some known weaknesses, such as being defenseless against naval units when submerged since Ythotha doesn't have torpedo tubes. Overwhelming an Ythotha with dozens of Bombers or Gunships is a great idea to bring this colossus down.
"Ahwassa" Experimental Bomber: The Seraphim's main weapon for all invasions immediately following the Infinite War. It is the most expensive aircraft compared to counterparts such as the CZAR or Soul Ripper. In the center of ship a negative tactical bomb is created, that deals considerable damage, enough to clean out unshielded bases within one bomb and enough to assassinate Cybran or Aeon unupgraded ACUs. It is armed with anti-air Autocannons strong enough to take out a few T3 Air Superiority Fighters. The true strength of the Ahwassa is that it moves faster than either the CZAR or Soul Ripper making it the fastest experimental unit. The Ahwassa's payload has some disadvantages in that its bomb recharges very slowly and must set up another bomber run before it will attack again, leaving it vulnerable to many bundles of anti-aircraft defenses.
"Yolona Oss" Experimental Missile Launcher: The most powerful yet most expensive unit in the Infinite War. When it's constructed, it creates the most damaging strategic missile seen. The missile, when launched, needs at least 2 Strategic Missile Defenses to neutralize it and if the missile lands will create an explosion that covers roughly six and a half square kilometers, with nothing having the ability to stand against its power. Yolona Oss' damage potential is extreme and completely unmatched, even by the durability of a Megalith or the Galactic Colossus, and can massively tip the game in favor of the Seraphim. Additionally, the missile is very cheap to produce and fast enough that adding additional engineers isn't necessary. The only major downsides of the Yolona Oss are the price to construct it and the number of missiles held. The Yolona Oss costs immense amounts of energy, mass, and time. Unlike the Strategic Missile Launcher that holds up to 5 nuclear missiles, the Yolona Oss holds only one at a time.