The Rat Farm is a somewhat dangerous zone full of auto attacking rats and human rat keepers.
The Rat Farm can be accessed through a hidden entrance off The Soake in Ankh-Morpork.
The Rat Farm is an instanced dungeon with a randomly generated map. Generally the Rat Farm generates with between 3 and 6 levels but more and less are possible.
These come in a number of varieties including Fat, Large, Round and Sleek. They auto attack on sight. Although a week NPC they are considerably stronger than the other rats in Ankh-Morpork including Evil Rats. Although not dangerous on there own there can be 5 of them in a single room which can fairly quickly deplete your health if you aren't prepared for them.
These are dwarfs tasked with keeping the rats. They will protect any rats in the same room as them. They can perform very week specials but are generally not a very strong NPC.
These are groups of between 3 and 6 rats (indicated by the "tail" count) that are tied together by a silver ring. The silver ring has rubies embedded in it, the number of rubies indicate the number of tails the rat had. Rat Kings are the least common NPC in the Rat Farm and most instances of the Rat Farm don't contain one. The rat kings are much harder to kill than the other NPC's in the rat farm and have a couple of special attacks. Firstly if you kill all of the other rats in the room with them they will "call" and new rats will run in an assist the king. There other special attack is a "squeek" which pierces the mind and does approximately 100HP damage. This damage appears to bypass shields and other defenses. These attacks can be triggered in fairly quick succession resulting in a fairly large loss in hitpoints. Once the Rat King is killed, the rats that made it up scatter to surrounding rooms.
There are a number of traps which trigger automatically upon entering a room.
A button is depressed, the floor creaks and then if you don't leave the room quickly enough you fall through a trapdoor loosing some health. You will also find yourself somewhere else in the Farm, this could be one of the levels below you or even somewhere else on the level you are currently on.
A button is depressed, a huge rolling boulder falls in from above and if you don't leave the room quickly enough you take a decent amount of damage. The boulder will continue to chase you from room to room unless you leave to a different level.
A slit in the wall open then shortly after arrows are fired at you doing varying amounts of damage. These can be deflected with parry or dodged. Alternatively you can leave the room and wait form them to finish firing before re-entering.
You will see a line in the room description indicating that your way is blocked for an exit.
A tripwire is stretched across the southwest exit at around knee height.
Trying to leave in that direction before cutting the tripwire with a sharp implement will fail, causing some damage.
cut <tripwire> with <object>