Over centuries of isolation from the world above ground, the changelings have made use and allies of many other creatures for both species' benefit.
Several species of herbivorous ants produce antibiotics for the changelings. In return, the changelings protect the ants from parasitic wasps and insectivorous rodents, and safeguard their fungal farms from more aggressive species outside of the hive. These ants also serve as farmers for some of the changelings' other symbiotic partners. All of them share a single colony, with some species existing in a monogyne form, and others observing a polygyne from.
A single colony of eusocial fireflies lights up the hive through a long series of tunnels built from translucent materials into the ceiling and walls. They also defend the ants in tunnels too small for the changelings to access. In return, the ants provide food for them. While this colony overlaps with that of the ants, their many queens are housed in a separate chamber from those of the ants, and there are many tunnels that connect to this chamber from which the ants are prevented to enter.
My associate tells me that the changelings have also domesticated other things, such as a flavor of apples unique in all the world, grown in the prisoners' city.
They have pacified many beasts of the Badlands, such as the basilisks and the tatzelwurms, and even tamed some of each species. They are not trained for war, but to dig tunnels to expand the hive, as they know the subterranean world better and can dig faster than the changelings ever could.