The brooding caverns are the network of caverns on Alternia which house the Mother Grub and her attendant jadebloods, as well as the Troll brood; eggs, wigglers, cocoons and young trolls, all in the first part of the troll life cycle. The laying Mother Grub, (or Grubs, although it is unknown if more than one Mother Grub is fertile at the same time), resides in a vast central cavern, receiving regular deliveries of genetic slurry carried in filial pails by imperial drones.
Its structure resembles real world ant broods, as well as those of many other related insects - excluding the obligatory troll weirdness.
Young trolls emerging from their cocoons must face the Trials, a set of challenges designed to weed out the weak. Many trolls die both during this process, during their time as wrigglers, or due to deliberate culling. The brooding caverns are also where surviving young trolls are selected by their Lusii, and form their initial caretaker/charge bonds.
This location is mentioned frequently throughout Homestuck, although it was not visited in canon until the release of Hiveswap Friendship Simulator: Volume Three. Bronya Ursama is the head attendant Jadeblood to her section of the brooding caverns, seeing to the Mother Grub near the city of Thrashthrust. As such, her Friendsim route takes place within the caverns. Hiveswap Friendship Simulator: Volume Eleven also features the same location in Lynera Skalbi's route.
The brooding chamber of Bronya's Jadeblood enclave houses a (the?) Mother Grub, her attendants, troll young in various stages of development, and is also frequented by Lusii seeking new charges. The "chamber" is more accurately a cavern the size of a small city, and is shown to be a bustling hive of activity. The fertile Mother Grub resides at the center, constantly laying new eggs from her sphincter. A convoy line of imperial drones carry her filial pails, allowing her to imbibe genetic slurry that comprises the genetic origin of her young.
Wigglers hatch from the eggs, and eventually come to spin their cocoons on the cave walls and stalagmites, before these cocoons in turn hatch into juvenile humanoid trolls. Despite the importance of these young for the continuation of the species, the nest inhabitants as a whole do not seem to pay too much mind to their safety. Drones habitually cull young, kill anything that annoys them, or even step on newly hatched trolls or eggs entirely by accident. Indeed, it is apparently traditional to allow young to be killed in large numbers even before their trials upon emerging from their cocoons, so as to, supposedly, ensure the preferencial survival of the strongest and fittest. Bronya's Jadebloods are atypical in that they often stray from this tradition and care for the wigglers; this however would be highly discouraged by society, and as such they keep their activities covert.
This chamber is also frequented by a diverse proliferation of Lusii, for which it is the stage for their selection of their charge and the forming of their symbiotic caretaker bond, once the charge in question has completed their trials.
Bronya's Jadebloods break from popular tradition, and maintain a wiggler nursery where they care for wigglers which are sick or injured, allowing them to recover before releasing them back into the brooding caverns to spin their cocoons. The nursery is a building located within the caverns; the interior is filled with cabinets of medical equipment, anatomical diagrams of wigglers, and "kiddie-pools" of Sopor Slime to house said young.
The care for injured young in this manner is not "technically" illegal but is stated to be contrary to tradition and would probably be highly frowned upon by most trolls in power. Bronya faces a conflict between her desire to maintain the nursery and care for injured young and her desire to keep it on the down-low so as not to draw the attention of the Highbloods to her enclave, a line she walks by projecting a neutral facade on the controversy and outwordly voicing her approval for the traditional methodologies.
Lynera's Study Cave
In Lynera's route in Volume 11, she kidnaps the player and ties them to a chair in a smaller cave. She has turned this cave into a smaller area to study, and has a bookshelf and many pictures of Bronya. An Iron Maiden with jade blood coming from it, a spiked club with various colours all over it, two troll skulls and what appears to be bright red blood on the floor can be seen, but no mention is made to why they are there. Judging by the pictures of Bronya and Lynera's reluctance to tell her about her crush on her, it's likely that she keeps this place a secret from the other Jadebloods.
The brooding caverns and Mother Grub are traditionally tended too solely by the Jadeblood caste. The details of other Jadeblood enclaves, their location, and their role in attending to the Mother Grub is unknown. However, Bronya is the leader of an enclave located in the caverns near the city of Thrashthrust. While other members of the enclave besides Bronya are not met directly, Bronya speaks at length of her matronly care for “her jades”. The enclave seem well practiced at managing any crises that may emerge in the brooding caverns, using teamwork and numbers to get unfortunate situations - such as those involving rogue Lusii as seen in Friendsim Volume Three - under control.
Under Bronya's direction, the rest of the enclave assist in the care for injured or sick wigglers in the nursery.
- Main article: Mother Grub
While other Mother Grubs, such as Kanaya's virgin Mother Grub lusus, do exist, the one known fertile, laying Mother Grub resides within the Brooding Caverns near Thrashthrust (at least according to Hiveswap Friendsim's ).
The role of the Mother Grub is vital to the troll race, as she is the sole progenitor of their young, although the precise biological relationship between the Mother Grub and the troll race is unknown. Bronya's enclave dutifully care to the needs of the Mother Grub, resolving crises that threaten her while she undertakes her perpetual duty of egg-laying. The Mother Grub seems to remain static inside her brooding chamber, receiving genetic slurry from drones and laying eggs. If she ever ventures elsewhere, this is yet to be seen.