Tevilar IV-5, the impossible world
In the thousands of dimensions the I.D.E.A. surveyed, most were bland and uninteresting except for prospectors and some passionate geologists. Some others were gems vitals to the expansion of the Dominium, through their people or characteristics. Some were utterly weird. And one of them is Tevilar IV.
Something that cannot exists
Tevilar IV-5 is not supposed to even be there in the first place. The configuration of the dimension prospect calculators makes it jump from one possibility to the other, without missing one. Both Tevilar IV and Tevilar V were existing dimensions of mild interest, rich in metals and minerals. Nothing else was found with this configuration and the I.D.E.A. moved on to another opportunity. Until an alert was raised and the algorithm signalled a new dimension has been determined to be between the two. Named in the rush Tevilar IV-5 as a dimension halfway between Tevilar IV and V.
The first explorer was hesitant to cross the gateway to what seemed to be an anomaly beyond understanding. The probes did come back, though some of their parameters seemed to be brought back to factory defaults. Still, Caesar Lucifer was not one to back out from duty. He stepped into the portal and arrived in the Impossible World.
Something that should not exists
On the other side, Caesar found a familiar world, yet so odd. He sighted things he had seen in history books: the Eiffel Tower, the Coliseum and the Taj Mahal, all gathered in a city that looked like ancient New York. For some reason, this historical nonsense is what struck him first, not the fact that he was flying without calling out on his power. He was also upside down, with the city spreading above him while the centre of gravity was under his feet. Chunks of cities were flying perpendicular to each other, roads turning in straight angles with cars driving on transitioned seamlessly.
People there were similar to Terrans, genetically that is. They shared the same genetic markers as early 21st century folks. Such a thing was never seen before, even the closest modern human civilisation had vastly different markers, even if they were physically identical. The only conclusion was that either a group of 21st-century people encountered a dimensional anomaly that projected them here, or that the Impossible World somehow mirrors Terra five centuries back.
Another feature of the impossible world is that no technology that is not native to it fails to work properly. That applies to high-tech like Z reactors and biofluid, but even the simplest cog gets knocked out of its axis when trying to turn. This made the integration of the Impossible World to the Dominium harder than it was supposed to be. Technological progress could not be brought and change the world, even Inter-Dimensional Train and gateways had to be engineered on-site with crudely primitive tools.
Another planet-wide city?
Is the Impossible World an infinite city? Nobody from the exterior has ever been able to find a limit to the urban expanse, although the locals claim there is one. The world itself is ever-changing, with chunks of the city vanishing into thin air only to reappear far away months later while no more than a second had passed for the oblivious inhabitants. No attempt at charting the place was successful, as even the best cartographer could not make sense of the place.
One thing is certain, that the city is insanely big for the period it seems frozen in, and that the people living in it are not clones of each other. The city is estimated to be about a twentieth of Terra's surface, nonetheless, it is but an educated guess and if there is indeed a whole world beyond, the real extent of the dimension may be unfathomable.
With Murphy's law in effect, the extent of the I.D.E.A.'s troubles was greater. To their surprise, not all of the very real inhabitants of the dimension were happy to join a greater scheme of things. And for once, it was not possible to quell the hostility with sheer strength. No weapon or armour was effective, and the only way to fight off the rebellion was to use the antique firearms manufactured in the city. Even explorers had to step out of this conflict, as the power of the Alcyers was misbehaving and the Icarryans had trouble keeping the link to their glykren.
The I.D.E.A. managed to convince some of Tevilar IV-5 inhabitants to join its side and take part in the war against the forces that took refuge in the Italian part of the city. The campaign of Roma was one of the bloodiest the agency took an active part in, with over a million death on each side. By the end of the day, they came to a truce when the Alternative threatened to join the conflict with the Romans. The terms of the peace treaty were that the Impossible World would not be integrated to the Dominium and neither it nor the I.D.E.A. could build any place of power there, and in exchange, they would let them stabilise their gateways and allow trade and migrations in the dimension.