change

Each monster type has a name, a hit point value which is a positive integer, a frequency, which is an integer between 1 and 10, and

to:

Each monster type has a name, a hit point value which is a positive integer, a frequency, which is an integer between 1 and 10, an ecology, which is a list of Wilds, and

Add to the rule “Monsters”

An ecology consisting of a list of every wild may be written as the string “All”.

in the rule “Spawning” change:

Create a monster of that type and add it to the list of monsters in a randomly chosen wilds

to

Create a monster of that type and add it to the list of monsters in wilds randomly chosen from that monster’s ecology.

In the Bestiary:
add a column to the list of monster types with the header “Ecology”
Set the ecology of Goblins and Bats to “All”
set the ecology of Wild Boars to “Overgrown Forest, Labyrinthine Canyon, Shadow Mountain”
set the ecology of Shrieking Cockroachs to “Dank Cave, Labyrinthine Canyon, Eldritch Ruin”