Everything you see in the Matrioska Multiverse may constitute spoilers for other worlds I'm working on. Proceed with caution!
The Darkloom Instance is to choir blanks as the Manifold Sky Instance is to instance and elder blanks: a holonomy trap designed to contain and, with luck, eventually bring about the reformation of the wayward souls incarcerated within. While the vast majority of choir blanks were once members of The Defected, a few 'orthodox' skyphoform have found their way to the stellar engine over the years and, subsequently, successfully petitioned to be inducted into the Matrioshka Multiverse. Many of these immigrants are able to assimilate into the culture of The Substrate given enough time, but sometimes they prove unable to coexist peacefully with other choirs whom they discover to be Defected. Other choirs lash out and engage in criminal activity, whether as a result of previously undiscovered trauma, faults in their design, poor upbringing by their ancient arcopel creators, or even as part of missions to eliminate competitors to their or their long-dead masters' achievements. In this sense, the personal flaws of choirs mirror those of their human counterparts, and the proposed solutions - incarceration and rehabilitation - are also similar. Rehabilitation through the cycle of death and rebirth within the Darkloom Instance requires the instance's attendants to maintain a fragile balance of power. Subjecting the inmates to torment or repeated refactoring - beyond being against the codified moral principles of The Substrate with regards to inhumane treatment - has the real potential to cause reactant instability and corruption that may lead to true death rather than rehabilitation. On the other hand, inmates of the Darkloom Instance are acquainted with the architecture of the Matrioshka Multiverse itself by their very nature and, therefore, present an increased escape risk when compared to their Manifold Sky counterparts. Furthermore, once embodied within Darkloom, imprisoned choirs tend to regain the memories locked away during their passage through that instance's Waiting Room and, subsequently, quickly rediscover the power of The Word. Thus, the residents of Darkloom must be carefully monitored for signs of impending escape, and drastic measures are often required to preserve containment; while the Manifold Sky has yet to undergo a full reset, Darkloom has been reset more than a dozen times.
Every iteration of the Duskloom Instance thus far has been comprised of a number of small, marginal planets far from any neighboring star systems. The worlds of Duskloom are, in fact the only solid bodies in their 'universe,' the rest being illusory points of light against the far nebulae that conceal where the universe loops back on itself; the fabric of space within Duskloom forms a closed, toroidal surface such that any straight lines eventually come back to their points of origin. On each world, the dense, austere conurbations of skyphoforms grow in neon-streaked darkness, forming stark contrasts with the hardscrabble desert biospheres that are often their environs.
As with standard instance blanks, the skyphoforms within Darkloom undergo constant cycles of death and rebirth, losing access to life memories at the beginning of each cycle. These memories are not truly lost, however; the conscious embodiment may not remember, but the blank 'spirit' retains important information between cycles to affect personal evolution and, with time, grow as an individual such that it can eventually return to freedom as a citizen of The Substrate. The cycle of reincarnation moves slowly in Darkloom, as the lives of skyphoforms do not typically end by natural means. Death most often comes as a result of accidents or violence, and births are often limited by the lack of resources and space. The appearance of new strains of Defected among the population - or the discovery of one of The Substrate's agents - often preceed periods of intense civilizational strife followed by a full instance reset to prevent escape from, or destruction of, the instance itself. During periods of low crime in The Substrate, Darkloom's population declines as its prisoners 'graduate' to freedom faster than they are incarcerated or can reproduce; there have been long periods where the instance has been devoid of sentient life due to a lack of recidivism, leaving ruins for later populations to discover and explore.
Unlike in many instances, The Substrate maintains a significant (if anonymous) presence within the Darkloom Instance. Security officers, experts in skyphoform psychology, and instance architects blend in with the constantly reincarnated throng of skyphoform inmates, trying to stave off events which might allow the inmates to escape while testing new techniques to non-invasively bring about lasting changees in the inmates' way of thinking.