The Rat has a simple economy based on apple gathering and lumbering wood. He also constructs a stone quarry and a low number of workshops to supply his army with weapons. He buys weapons in small numbers when lacking them in the armoury. He has low taxes and a good reserve. He has a low population so not much food is consumed.
The Rat doesn't use much stone for walls and his troops are cheap to hire, meaning that the simple economy serves the Rat well.
The Rat is very inefficient in both attacking and harassment. He uses a small number of spearmen and archers (mostly sending them one by one) to distract enemy workers, this can be annoying at the start of a game if farms and quarries are not well defended.
When it comes to attacking a castle, the Rat uses a brute force of spearmen and archers in a big group. Unlike the Snake, the archers are not a danger to archers on walls as they are few and deployed in tight formation. He also does not use any siege equipment, so he is just lacking any success against a mediocre defense. He does however, usually attack earlier in a game than any other AI lord, so his initial attacks can be annoyance to his enemies if they are slow to completely defend their castle. Eventually if he has enough gold, the Rat has the capability to build up large armies exceeding 100 spearmen, but there are still only a few archers to accompany them.
The rodent builds castles with random shapes and layout. Sometimes he encloses all of his buildings, but most of the time they are just left out in the open. His walls are fortified with or without any towers and single archers are spread out on wall sections. A group of spearmen patrols the Lord and important areas of the castle.
There is one defensive advantage with the Rat's castle design. This is the fact he does not usually situate his bowmen on towers, but rather on the walls. This means that his enemies cannot leave towers in a permanent crumbled state, unlike with other AI characters in the game, to prevent his archers from ever firing upon them again.