Herbs are guaranteed in the Big Room which leads to the dilemma of whether to stay and harvest herbs or flee from the constant onslaught of monsters.
Petri Sihvola has discovered a way around this dilemma.
His post from RGRA:
With a bit of planning and minimal amount of equipment, it's possible to fight monster generation, to the point that no new monsters appear on the level for the rest of the game, letting you harvest your herbs in peace.
In order to achieve the desired effect, using this particular solution, in this particular level, one needs...
* a breeder
* 14 doors, forming an enclosed area of 8 × 5 or 7 × 6 squares, or 1-13 doors and a method of digging, enclosing an area of at least 40 squares total
The first thing to do is to find a breeder and leave it somewhere, until you have the necessary equipment. For those who like to do things the alternative way, and are in a position to do so before finding a naturally generated breeder from a nearby CoC level (or the Big Room itself), find/create a corruption trap and lure a regular rat over it... to generate a chaos rat... which is a breeder.
I'll provide two examples on how to proceed from here, depending on the amount of doors you're planning to invest in this.
Example 1 (14 doors, no digging):
Choose a corner that would disturb your herb patterns the least, and create the doors, like this:
#.......... #+++++++... #......+... #......+... #......+... #......+... #......+... #......+... #......+... ###########Now, get the breeder from wherever you left it, and lure it inside the box. Close the doors, so that the breeder won't escape and wait outside. Protect the doors from random passers-by and observe the occasional popping/burping sounds.
Once the amount of breeders reaches 40, all monster generation in the level stops. Start to wander further from the box and kill the remaining monsters from the level.
Example 2 (1 door, some digging):
At first, it would seem that the big room has no walls to dig, but upon further investigation this appears to not be the case. You can dig one square left, one square up, three squares right and two squares down, into the wall. This leaves the lower right corner as the obvious choice to start digging, and the two-square wide corridor in the right side allows for getting around the initial breeder without needing a second exit. Enclose a 40-square area...
#### ####..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ...#..# ..+#..# ###...# #.....# #######...get the breeder inside and apply the same method as in the first example.
If everything went well, you're now looking at a completely peaceful, guaranteed herb level, which is guaranteed to be in a non-corrupting zone.