8' large beetles of Pandemonium with one interesting property: they take on some of the appearances of whatever it was they last ate each time they molt. Not enough to disguise themselves, mind you, for example "Having eaten a horse, the murska's carapace gradually molts to reveal the dapple-grqay hide of a horse beneath, stretched awfully over the cursed insect's shell." As it gets hungrier, the new skin sheds to reveal the "true" form beneath.
Another interesting thing is that, while normally mindless hungry insects, if they eat something sentient, they take on the intelligence and memories, although not spells or skills/proficiencies or whatnot. But some murska deliberately seek out intelligence once they've tasted its fruits, building "larders" of sentient victims to feed upon when they use up their current skin.
* There's a Murska in Sigil who offers the criminal element a simple deal: give it somebody intelligent to eat, it'll tell you any of that person's secrets you care to know. Cheaper than hiring a psion or diviner by far, if you're callous about the sanctity of human life, but we are
talking about the criminal element here. Business is going well until a friend of one of the PCs ends up in the beast's semisecret larder.
* The PCs, exploring Pandemonium, lose a few henchman. Until they come back, skin stretched tightly over insectile form. Right after the Murska have fed, the nature of that which they fed upon is still strong, and the murska aren't looking for a fight, they just want "their" old jobs back, and protection from the dark and scary twists and turns of Pandemonium. But as time passes, the insectile instincts grow stronger and stronger, unless the PCs can find some way to magically halt the reversion process. Or they could just kill the insects before that happens, but then they'll have to listen to cries of "No, master! Don't kill me! Please, I'm sorry!" and such. Because you, the GM, are an asshole, as well as interested in exploring philosophical questions of the nature of identity.
* "Revolutionary League legend holds that the beasts are the spirits of their lost brethren, forever assuming the identity of others. Desperate Anarchists sometimes bring their concerns to the "revolutionaries who have been" in hopes the god-beetles will grant them aid."
There's any number of ways to use that, but let's up the ante a little bit. An extremist sect of the Anarchists wants to try something both hideously blasphemous and a phenomenally bad idea: feeding a Murska some bits taken from a dead god's corpse in the Astral. The PCs hear wind from the plan by somebody sympathetic with ties to the cult, unwilling to act personally against them, but worried about the potentially catastrophic consequences such an action might have.