The meridian fortress is a critical piece of interplanetary infrastructure that takes shape as a unique building type, there are nine in all, six of which are located at the exact equilateral exit-points of the planet's X, Y, and Z axis. One is located at the core of the planet. And the remaining two are located at the core of the sun and the moon, respectively.
Each fortress is an entirely unique building, however, all nine fortresses share a set of fixed characteristics that clearly distinguish them from all other known building types. First and foremost they are not passive structures as are all other buildings in / on neotoy. Their architecture is specifically designed for maximum lethality, every floor, every layer, every aspect of each fortress is loaded with intricate and deadly traps. Additionally the types and methods of these traps are unique to each fortress and are capable of changing in limited yet insidious ways, in other words there is no way to 'learn' them.. unless you have a very, very long time, and many, many lives.
Secondly, due to their geographic location, each fortress is specifically designed to take advantage of and exploit the various themes and environmental conditions that are unique to the region. For example, the ruby fortress
a.k.a. red fortress located in the center of the hot region
uses a plethora of photolyths
to fill the fortress with countless deadly lasers and optical illusions that will lead all but the most discerning to their deaths.
Naturally the primary goal of a meridian fortress is to protect and prevent access to the chromachron
socket that is hidden deep inside at the inner sanctum. It should be noted that it's not impossible to breach a meridian fortress, nor to learn their secrets over centuries of study, once you determine where the consistent safe-zones are located inside a fortress you could theoretically live there. Once inside there is no place safer in all of neotoy; that is as long as you don't forget how to get out alive!