Thousands of years before the Involved Species' recorded history, an Involucra race named the Veil had created vast spheres from an unknown but highly resilient substance consisting of several layers, interspersed with a tracery of tubes and towers which maintained the spherical integrity of each layer. It was supposed that each of these layers were to contain some form of superfluid, distributed through the great towers, for reasons unknown, though it was supposed that once all the Shell Worlds, which originally numbered over 4000, were activated it would create an energy shield around the whole galaxy. For similarly unknown reasons, the Veil disappeared, leaving the Shell Worlds derelict. Some time later, a race called the Iln attempted, again for reasons quite unknown, to destroy the Shell Worlds. They were somewhat less than successful, and like the Veil, disappeared.
Some time later the remaining Shell Worlds, now numbering around 1000, were "discovered" by modern races, and it was realised that they could provide enclosed environments for a number of species, once several protective systems, both Veil and Iln, had been bypassed. That several of these systems activated or reactivated, eradicating populations or entire races housed within their Shell World lead to one of the Shell World's more evocative alternate names; Slaughterworlds. The shells were fitted with thermonuclear artificial stars which either stayed fixed ( Fixstars ) or rotated (Rollstars ) around the ceilings of each shell on semi-regular paths. Access between the shells was through the huge 14-kilometer wide access towers using Scend Ships .
Several Shellworlds were home to Xinthian Tensile Aeranothaurs, ancient creatures who resided at the core of the Shellworlds, generally perceived to be retiring from the galaxy and galactic concerns. The Aultridia and Oct claimed Sursamen around the same time. The Oct believed themselves to be directly descended from the Veil, and referrred to themselves as "The Inheritors", though in reality their relationship to the earlier species was generally discounted. The Aultridia, descended from parasites which lived on the Xinthia, considered themselves more deserving due to their connection to the creatures living in the Shellworlds' cores. The ensuing conflict was localized to the Shellworld and both were eventually assigned joint protective custody of the world's access Towers by the Galactic General Council. They were overseen by the Nariscene , and the Morthenveld , in whose space Sursamen lay.
Its 15 levels shelter various species, some of them live in environments very different from earthlike environments. The various levels and the towers that provide transport are controlled and mentored by three species; The Oct, The Aultridia and the Nariscene, who are designated overseers of the shell world, with the participation of the Morthenveld. Levels 8 and 9 are provisioned for occupation by human-basic lifeforms - the Sarl , mentored by the Oct, live in level 8 while the Deldeyn , mentored by the Aultridia, occupy level 9. The remaining levels are occupied by a variety of non-humanoid lifeforms in various environments taylored to their needs.
Sursamen occupation by level 
|0 (surface)||Vacuum / habiformed||Nariscene / Baskers / others|
|4||o2 atmosphere, oceans||Cumuloforms|
|5||Methane shallows||Kites / Avians|
|6||Higher gas giant||Tendrils - Naiant|
|7||Methane ocean||Vesiculars - Monthian Megawhales|
|8||Land (o2 atmosphere)||Sarl|
|9||Land (o2 atmosphere)||Deldeyn / Sarl|
|10||Mid gas giant||Tendrils - Variolous|
|11||Methane ocean||Vesiculars - Monthian Megawhales|
|12||Lower gas giant||Swimmers|
|13||Water / slush matrices||Tubers / Hydrals|
|14||Ice / water||None (dark)|
|16||Core - solid||Xinthian|