My wife got me Halo 5 for Christmas, and hot damn what a ride! Great fun to play, but from an over-arching meta perspective it showed us the civil war the Elites have been fighting for almost as long as the Covenant has been gone- the Blooding Years, as they call it. With a surplus of Covenant vessels from Halo: Fleet Battles that are begging for that cool blood red color the Swords of Sangheilios use, and seemingly recent confirmation that the "new" Sangheili ships from Halo 5 will be realized in miniature form in the (hopefully near) future, I wanted to get a head start on a little background for the timeframe these ships appear in. Additionally, my earlier post describing the UNSC's rump Fourth Sector for campaign background purposes has consistently been the most popular post on this blog, so it seems there is an appetite for such content among readers here. It's my earnest hope that means I'm inspiring some of my fellow gamers out there.
The primary Sangheili colony in the Csolek system, Ero'deolos was one of the outermost worlds of the original Sangheili domain until the War of Beginnings. A San'Shyuum attack in the war's early years decimated the planet's defenses and forced the population to evacuate back to Sanghelios. For a time, the Forerunner Dreadnought used the Csolek system and it's many moons and planetoids as a hiding place, baiting two seperate Sangheili warfleets to overextend themselves and be defeated while searching the vessel out.
After the Writ of Union was confirmed, Sangheili colonists returned to Ero'deolos to find a small San'Shyuum enclave had been placed in the main keep on the planet. Though allowing the Sangheili to return to their original settlements, the San'Shyuum maintained their enclave in the heart of the Sangheili colony, a rarity in the Covenant. This arrangement lasted throughout the Covenant, having an impact on both races.
Elites from Ero'deolos are noted for their increased tolerance for other species, an attitude forced by the close proximity of the San'Shyuum. Many Elites from elsewhere in the Sangheili sphere deride this tolerance as a predisposition for grovelling- a belief that was not helped by the San'Shyuum preference to elevate the more easily-influenced Ero'deolos Elites over their peers. Many Sangheili conscripted from here found their way into the Ministry of Preservation, dedicated to preserving the Covenant against internal strife.
For their part, San'Shyuum from the planet were notable for their more belligerent attitudes and stubborness, and were known to advocate for the Elites in interspecies disputes with inappropriate vigor. As a result, they rarely rose to positions of higher authority throughout their history. Indeed, at the dawn of the Great Schism, most Prophets from Ero'deolos were imprisoned or worse for their suspected pro-Elite attitudes.
Ero'deolos itself was in time developed into a regional powerbase for the Covenant, being at the edge of Sangheili and Covenant space at the time, and helping expand the empire's influence deep into the Shining Marches. To facilitate this, the Prophets directed a modest shipyard be built in orbit to service exploratory and colonization fleets in addition to contributing warships to the military. Though few Forerunner sites or artifacts of any importance were found in the region, the Shining Marches were home to several lesser species that at least paid homage to the Covenant, if they were not a part of it's Fringe.
During the Great Schism, the Ministry of Preservation forces based on Ero'deolos experienced their own internal implosion when the fleets stationed over the world began fighting each other. The Jiralhanae-led and heavily reinforced Fleet of Truculent Compassion initially made great headway against the Sangheili-led Fleet of Relentless Zeal before the Fleet of Considered Reprisal arrived to reinforce the Sangheili and drive off the Brutes. Though victorious, the Sangheili forces were badly damaged, prompting Thel 'Vadam's nascent Swords of Sangheilios to send reinforcements to the world, though these were not warmly received. The Swords themselves were guilty of making insinuations that Ero'deolos was collaborating with the Prophets, a popular belief at the time. The resulting animosity saw Ero'deolos largely on it's own against nearby Brute forces, and soured several native keeps against the Arbiter, later driving them into Jul 'Mdama's camp.
'Mdama's Covenant has largely kept Ero'deolos' forces in place, both to protect the still-operational shipyard over planet and to prosecute war against the few keeps on-world that have professed loyalty to the Arbiter. Spies loyal to the Arbiter have suggested that not all of the Covenant's supporters here are truly invested in the movement, and may in fact be hiring their forces out to parties able to pay for them. It is unknown if Jul 'Mdama is aware of these mercenary operations, or if he would even be overly concerned.
For his part, the Arbiter has dispatched a taskforce from his Swords to support the loyalist keeps and tie up Covenant forces in the region. This taskforce, Bladesworn, contains many of the Swords of Sangheilios' remaining Covenant-produced warships, being the more capable multi-role vessels to prosecute the campaign, and best able to engage the warships of the Ero'deolos Covenant fleet.