Since the fluff writing takes a long time, here's some teasery bits to add some context to some of the units that appear in this book.
Berserker infantry: a piratical combination of drugs and crude brain surgery to create crazed shock troops to frighten the populace of their targets.
All the generically named combat support vehicles: Generic combat vehicles for worlds that can't build or acquire modern combat vehicles. Most of them would also work pretty well in a pre-battlemech or early battlemech age of war setting
ICE battlemechs: Just battlemechs that might be relatively common in the periphery refitted with internal combustion engines, because fusion engines can be hard to come by.
Cosmos: A bimodal LAM, largely an enigma to the Inner Sphere, but it seems to date back to the Star League era, and is being operated by a relatively unknown spaceborn group in the deep rimward periphery. When encountered, they tend to be peaceful, offering trade and advising travelers to stay away from the California Nebula. The concept of the UC variant is a shameless ripoff of the
Crane Utility LAMDigger: A combat industrialmech originally built on the planet of Goldbluff, which has slowly proliferated into the the deep periphery as a cheap garrison mech.
Rambler: A remnant of Amaris' Secret Army. The ammunition bay is located directly under the pilot and has a habit of exploding.
Rockhammer Industrialmech: A mech for mining in hazardous environments and a predecessor to the Rockhound
Shadow Hawk 1P: A common (primitive) battlemech of the Kingdom of Plymoth
Shadow Knight: Totally not a Shadow Hawk in a fancy new skin. The new hotness of Lewis County
Koloss: The first (primitive) battlemech of the nation of Novyy Rodina
Lugh: A common battlemech of the nation of Dal Riata
Warthog: A tripod, a legend of the deep periphery, and a gag about how an interplanetary species is going to have trouble identifying terran animals.
Battlehammer: A heavy mech built by the semi-feudal world of Foxhaven, after it was done civil warring with itself.
Minerva Dropship: A Taurian dropship dating back to the reunification war that has managed to linger in the periphery.
Rapier, Vesper, and Jasper: primitive craft operated by the largely space-based Interstellar Confederation
Aquilla-Type Jumpship: There are already at least two canon examples of deep periphery factions operating primitive jumpships in the modern day, and Beyond the Frontier is going to add a couple more, so I included a late generation Aquilla.