Ah, Kaliday, city of Kalid-ma. I remember days (weeks? months?) of fun debating the 'sex-change' of the late Champion on the Dark Sun mailing list a few years ago...

First of all, there is a very good summary about Kalidnay on Nytcrawlr's site:

Kalidnay in our campaign

In our campaign, Kalid-ma was very interested in biological weapons such as the parasite plague he created (see Merchant House of Amketch). Taking inspiration from life-shaped items and diseases, he set out to create devastating, but controllable weapons with the power to self-replicate. Trials on animals, plants and humans were regularly made. Some of these victims are still around in undead form. Of the living things, the beetle-parasites were not the only ones that survived...

From Kalid-ma's Lab

Probably one of the most dangerous places to go on Athas are the remains of Kalid-ma's secret laboratory. Deep underneath the ruins, the laboratory has survived the disaster that shook the city pretty well. Formerly enforced by powerful magical and psionic barriers, these barriers have now started to grow weaker in places. Or maybe it is what is inside that makes them grow weaker?

Inhabitants of Kalidnay

Adventurers coming to Kalidnay might at first not notice the victims of Kalid-ma's experiments, as most undead look weird and unnatural. But there are living creatures in the vicinity of the city that exhibit unusual traits. These traits (the don't have to be negative traits) may also be found among the undead, e.g. an immunity against fire/magic/psionics or some form of quick regeneration. Some creatures may actually turn out to be dense swarms that have formed to resemble a creature. Think Michael Crichton's 'Prey'... ;)