The Mouse Guard itself is a brotherhood of mice who have sworn an oath to serve their fellow civilian mice in times of need.   From the wiki: “They are guides for common mice that look to journey without confrontation from one hidden mouse village to another. The Guard patrols borders, finds safe ways and paths through dangerous territories and treacherous terrain, watches weather patterns, and keeps the mouse territories free of predators.”  They also maintain the highly important “scent border” that helps ward predators away from the Territories, although some clever predators figure out the trick and must be dealt with by the Guard.

Mouse civilization’s technology is equivalent to medieval Europe between 800 and 1200 AD.  An important detail to remember is that they are mice and therefore unlike men.  They are not aggressive, in general, and their civilization is by nature more cooperative and defense-oriented.  When thinking of your character and its place in this world, it is important to think like a mouse.

The Mouse Territories

(from the Wiki)

The Mouse Territories is a rough and rocky portion of land locked by landmasses to the east and west. To the north of the Mouse Territories is the North Sea, while to the south-east is what appears to be a patch of small lakes and ponds. The whole area is heavily forested and blanketed with thick underbrush.

Situated around the edge of the territories is the Scent Border, while scattered throughout the Territories themselves are various mouse outposts, villages and towns each governed by their own local magistrates and mayors.

In the not-too-distant past, mice lived in tiny tree hollows, under logs, in stone cracks and other wayward, forgotten places. They lived scattered across the wild without community or support. They were hunted by predators, subject to harsh weather, and had few supplies to sustain them in the face of calamity. In fact, these mice were far more likely to perish from depredation, exposure, illness or starvation than live a long, prosperous life.

Against the overwhelming forces of nature, a few desperate groups made a stand. They staked a claim on a handful of safe patches of wilderness. As word of these safe havens traveled, other mice flocked to them. The most famous settlement grew quickly from a hiding place to an outpost to a fortification and, finally, to a citadel- fortified walls surrounding a prosperous town, defended by a dedicated guard. This place is now called Lockhaven, and it is the center of what is known as the Mouse Territories.

As Lockhaven became more and more secure, its guardians reached out to other settlements. At first, the Lockhavenites tried to bring everyone they found back to the safety of their city. Many came, but many would not. Other communities, perhaps less safe but still prosperous, had formed in the wild. They were reluctant to leave what they had begun, despite their precarious position.

There was a debate within the ranks of Lockhaven’s guardians. What to do about these other settlements? Should they be forcibly moved? Should they be abandoned? In the end, the guardians decided there was only one true answer: Lockhaven must use her strength to defend and support these communities. All mice must prosper or all mice will fail. Therefore, these guardians struck out to the distant settlements, marking paths and noting which directions gave them more cover, better viewpoints and quicker routes.

These brave, selfless mice quickly became known as the Mouse Guard. As their numbers grew and their protection was extended and came to be relied upon, the far-flung settlements did indeed prosper. Lockhaven itself changed as well. It became less of a bustling city and more of a central hub for the Guard. Eventually, the Guard took over the administration of the citadel completely.

The first mouse to organize the defense of Lockhaven was female. Thereafter, it has remained tradition that the Guard be commanded by a female mouse given the rank of Matriarch. She is in charge of internal affairs, governing the mice of Lockhaven and setting the Guard’s missions and patrols. The Matriarch determines Guard postings, what duties patrols are to complete and which areas in the Territories need the most attention. Beneath her are a cascade of captains and administrators who assist her in day-to-day operations and long term plans.

In the wilds between the settlements, all mice agree, the Mouse Guard is the law. But in the mouse towns, the Guard only has as much authority as that town’s government allows. Most settlements welcome Guardmice, but many defer to their own lawmice and protectors. Some places even force visiting Guardmice to turn over their weapons at the gates of their settlement.

Settlements

Lockhaven, Home of the Mouse Guard
http://mouseguard.wikia.com/wiki/Lockhaven

• Home to the Guard
• Most secure and fortified of all mouse havens in the Territories
• Used as neutral location for mouse leaders to gather for annual summit
• secure food storage for surplus reserve for all mice (and allies)

Barkstone, far to the West
http://mouseguard.wikia.com/wiki/Barkstone

• a large mouse city located in the far west region of the Mouse Territories. It is one of the nearest cities to Darkheather, and as such, maintains its own personal militia of armed soldiers to protect its citizens from immediate danger

Sprucetuck, to the SouthWest
http://mouseguard.wikia.com/wiki/Sprucetuck

• The home of mouse science and medicine
• Known for their counter-weight driven lifts, their glassworks, and metallurgy

Copperwood, to the South
https://mouseguard.fandom.com/wiki/Copperwood

• one of the oldest cities and is built inside and below a large oak, with paths and ladders and living spaces all the way up to its tallest branches. The upmost parts of the tree are utilized for a lookout watch, keeping eyes and ears out for for predators, the comings and goings of mice, and the weather. Tunnels underneath the oak lead to a waterfall and the mines. The city’s largest trade is mining and smelting of metals, mainly copper.

Oakgrove, to the SouthEast
http://mouseguard.wikia.com/wiki/Oakgrove

Elmoss, in the Western Reaches
http://mouseguard.wikia.com/wiki/Elmoss

Ferndale, a settlement recently lost to the Weasels
http://mouseguard.wikia.com/wiki/Ferndale

Mapleharbor, just SouthWest of Lockhaven
http://mouseguard.wikia.com/wiki/Mapleharbor

Port Sumac is a remote, seaside mouse town located on the cliffs of the North Sea 
http://mouseguard.wikia.com/wiki/Port_Sumac

Willowroot is the southern-most mouse settlement
http://mouseguard.wikia.com/wiki/Willowroot

Rootwallow, to the southeast, is one of the bigger, more “urban” settlements. (Sadly, there isn’t a lot of information about this city in the wiki or in the books I have on my shelf. )

Pebblebrook is a more recent mouse settlement in the westernmost reaches of the Territories. The town is situated just southeast of the entrance to Darkheather and is known for its stonemasons.