Troglodyte Lifecycle (spoilers)

Spoilers about the lifecycle of Troglodytes

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Bits and pieces of this has been revealed in the comic at various times.
Normal Trogs in the MoEverse have a relatively simple lifecycle: They live in damp caves, hatch out of an egg laid by their mother after incubating for a time in warm mud or some such, grow up, mate and produce more eggs. However, there are scattered around the Known World various sub-species, not all of which are sentient. The Humans of Yurpsland breed non-sentient ones to make a high-grade leather often used in shoes. (Sylvester at least wears a pair.) And yes, people being what they are, sentient Trogs have no doubt been used for this purpose, but even for brutally amoral folks, it's usually far more trouble than it's worth, as the non-sentient ones are much more docile. And tend to be larger than the sentient ones, producing more leather.
The Basement Trogs are all of the smaller sentient type, and what is happening with them is not normal for the species. At some point in later in their lives, most of them start to undergo mental and physical changes, growing larger (ie, up to Human size) and losing most of their intellect. Most females (and some males) die in the process of this. If the changed Trog doesn't kill themselves (often by taking The Plunge) or get killed, they grow more and more feral, usually retreating to The Fringes of the Basement.
Why this is happening is yet to be revealed. Telic the Helipath Healer is investigating the phenomenon, and never passes up a chance to dissect a Changed corpse. (Or well, any kind of corpse, but that's a different story..)