The outermost edge of expansion in any direction in the Terragen Sphere is often known as the Mobile Frontier, an ever-expanding zone nearly fourteen thousand light years across at its greatest extent, at the outermost edge of the Periphery. Of course the frontier has changed location gradually over time; during the First Federation for example the Frontier was roughly at the edge of today's Inner Sphere, while during the Version War the frontier was a little over a thousand light years from Sol.
In the Current Era the Frontier consists of many diverse and widely separated regions which are not in contact with each other, since the Mobile Frontier is consistently outside the reach of the Wormhole Nexus. However the different regions aof the Frontier do share certain characteristics, and also reflect the character of the zones immediately solward of their location, since they have grown out of those regions.
When seen over a period of several millennia these mobile Frontiers are not specific places, but they are marked by a specific kind of culture. As time passes by, the Frontier by its very definition changes location, but the memes remain the same. Since they are outside the Wormhole Nexus, and the largest Archailects cannot travel that far due to their vast size, the Frontier zones are outside of the reach of the Central Gods, and many of the people who inhabit these regions would like to keep it that way. Unlike Hiders which fear transapients and attempt to avoid all contact, the pioneers often retain many psychological and cultural links with terragen civilization, limited however by distance and poor communications.
The fundamental cycle of a mobile frontier is simple, but different circumstances may bring many variations. In the first phase the pioneers settle a system at the very edge of Terragen space. The starting years are often tumultuous, various polities slowly grow, but many parts of the system are entirely lawless, and many hardcore pioneers prefer it that way, relying only on their skill and wits to forge a living from the resources of the system. However, as time passes by, the system reaches the second phase. The polities slowly grow in size, as newly arrived colonists, and old entrepreneurs seek the protection of a larger group. If the system has only few resources these early polities may be in competition, but in most systems the polities spread to occupy power voids, rather than invading their neighbors' sphere of influence. However there are still plenty of empty spaces for the polities of one.
In the third phase the polities reach their largest extension. Though there are plenty of empty spaces left, all worthwhile resources are under the umbrella of a polity. While the free life may still be found in oort clouds or asteroid belts, the polities of one are constantly rubbing shoulders with the larger polities, and may be forced to follow rules and guidelines on which they have no influence. Somewhere between the second and the third phase, pioneers begin leaving the system for the new frontier. Reaching new worlds the cycle starts over.
The first and second phase worlds are the mobile frontier, with a population of hardy pioneers. There exist many worlds that fit the description of the first and second phase, however the mobile frontier culture is the pioneers and their exodus once the world reaches the third phase. Often many of the inhabitants of a mobile frontier have participated in dozens of exoduses over the past centuries or millennia, though in a few mobile frontiers each new exodus consists of an entirely new generation of pioneers.
The Kleinman frontier at the edge of Sagittarius Transcultural Cooperative space is a classical mobile frontier. Major clades are the Faber, Greenbound, Tavi, Grrol and Kleinman, but as is common hundreds of other clades are represented, either solo or in small groups. Over the last 2000 years, the frontier has traveled 1200 light years. Six times transapients' wormhole layers has overtaken the frontier to such a degree that pioneering became impossible, but every time the frontier has hitched a ride through wormholes and with transapients' colony ships to reach the edge again. The Kleinman frontier hosts a unique clade, the Kleinman clade, which only exists in the Kleinman frontier, having evolved into existence there during the last 2000 years.