Well the bad news is that I'm still not done with the abilities for radiant priests and umbrals. I know, it's taking a lot longer than usual due to IRL concerns and technical hurdles, but I promise it's getting there.
The good news? I finished up the mantis construct raws today, and I've got them to work pretty nicely. The description isn't quite finalized yet, but here are some screens.
Mantises (I considered "mantids," but "mantises" is, in fact, the correct plural) are made from a variety of familiar mechanical components. You'll need to make an iron chassis, advanced mechanisms, mechanisms, two iron pipes, a mechanical eye, and a few capacitors. The reaction will utilize a new slug-like domestic creature (called a "slimer," which looks a bit like Gary from Spongebob) as the platform for transformation, integrating it as part of the mantis control module. Of course, if this part is damaged, the mantis ceases to function.
Mantises also have some new parts - notably the three power generators, which are made of lustrum and mounted on their backs. Damage to a power generator will slightly impair the mantis, while damage to more than one will cripple it - much like a dwarf with a spine injury. This feature is still pretty experimental, so it may or may not make it into this release, depending on how things go.
Despite having four armored, but functionally integral components (where the spider only had the one - the control module), the mantis is a little bit stronger than the spider in combat, and also is able to be penned or pastured like any normal domestic creature, rather than appearing as "friendly." Currently, there is only an iron mantis available for construction, but steel, mithril, and possibly even better variants may be available in the future.
Spiders can be constructed out of bronze (already implemented) and iron (finished for next update). There are currently no plans for more advanced spiders, but this may change in the future.