Eressus

A binary system in the Alyria Sub-sector containing several habitable worlds, all of which orbit Eressus A. The system is currently facing simultaneous Tyranid and Ork invasions.

Planets

Aetolia

A temperate world with a mixture of biomes, Aetolia is known for its natural beauty. It was originally an independent world before being conquered by the Tertians during M37, after which the Eressian League was formed to defend the system from attacks by other human systems in the sub-sector prior to Imperial unification during the Macharian Crusade.

Capital city: Aeos

Aeos is a port city situated on the coast of the Viyosan Ocean. It has a substantial space port ten miles from the city centre.

Ork invasion

The planet was invaded by the self-styled Warboss Bonerippa. With Imperial elements already in-system countering the Tyranid invasion of Eressus Tertia, an Imperial response is hastily drawn together, comprising the Cobalt Scions Third Company, 31st Nightfall Ranger Regiment, several regiments of Krieg Death Korps, and Battlegroup 86. Even so, the ork numbers prove so substantial that military victory seems unlikely. The balance is tipped when Inquisitor Michael's ship Accipiter leads a kroot warsphere into the system, delivering substantial numbers of kroot mercenaries, and ordering the Imperial forces not to engage them. Despite early gains that heavily damage Aetolia's planetary defences, the orks are ultimately destroyed by the Imperial defenders. Towards the end of the conflict, the enemy warlord Bonerippa is hunted down and assassinated by a joint force of Nightfaller Rangers and kroot.

Eressus Tertia

This temperate world is usually referred to simply as Tertia by the locals. It has recently been invaded by a Tyranid splinter fleet. This invasion is being countered by the Imperial Guard, including regiments from Nightfall, with support from the Blood Angels and Cobalt Scions.

Inhabited moon: Trasenede

Eressus Tertia's largest moon, Trasenede, is capable of supporting life, featuring an atmosphere of its own and inhabitable, if highly seasonal, climates. It features a single large city, Iria, and several smaller settlements, mostly focused on the exploitation of Trasenede's vast forests and high levels of biodiversity. A Tyranid splinter swarm attacked the moon as part of the wider invasion of Eressus Tertia, with Cadian and Nightfaller forces redirected from Aetolia in the wake of Waaagh! Bonerippa in its defence. The early stages of the fight for Trasenede were desperate affairs, with the survival of the city of Iria, and with it the core of the Imperial defence, in doubt. Through a mix of firepower, ingenuity and sacrifice the city held off a determined alien assault, and the invasion was blunted days later after Nightfaller reconnaissance teams identified vulnerable spawning pools in the deep forests, which were then targeted and destroyed in the kind of commando raids their regiments specialise in - made possible in the face of formidable Tyranid resistance by heavier Cadian muscle. Had the Tyranids seized control of the forest moon, the biomass they would have gathered would have been strategically disastrous, with troubling estimates as to how this would have affected the wider war. While the alien threat on the moon was not entirely eliminated, their forces were depleted and their ability to reproduce hampered enough that the Eressan PDF were then able to hold Trasenede... At least with the Cadian 177th staying on in an advisory role.

An unsettling revelation in the wake of the battle for Trasenede was the appearance of a separate distinct subgenus of Tyranid bioforms starting to emerge within the same swarm. Ordo Xenos scholars indicate this may be evidence of the Hive Mind evolving in response to Imperial resistance.