For those who don’t have the Inner Sea Bestiary, petrified maidens are petrified women animating in undeath—the cursed handiwork of the wizard king Geb (and scribe Greg Vaughan). In your campaign they might have another origin, but there still should be some unfulfilled obligation or vendetta to explain their resistance to destruction. Since they are undead who present as constructs, unraveling how best to defeat them could be a nice mid-battle puzzle even for experienced parties.
(And yes, these could easily be petrified youth instead of maidens. Nor do they have to be virgins. But I found both to be useful hooks for constructing the following adventure ideas…)
The medusa witch Lariss was famous for acts of particular evil, including the Stoning at Achiss and the petrification of an entire nunnery. When she was slain and then raised from the dead (the work of adventurers and a blind azer henchman, respectively) the spirits of all those she had slain rebelled. Every maiden Lariss caught in her gaze animated and began to hunt her down. But they have no love for the living, either, whom they blame for their stony state, and will caught down anyone who gets in their way.
Even for a drow goddess, the Scorpion Queen is a particularly jealous deity. When a fane to Orpolia, the Skull Matron, was constructed in Alphez’dre, the Scorpion Queen commanded her clerics to bury the entire temple district in mud. Orpolia retaliated, raising her worshippers as petrified maidens. Wielding the traditional drow scimitars, they will hunt the depths until every living daughter of Alphez’dre is slain.
There is only one fiendish unicorn—the get of a semi-divine nightmare born under the Moon of Blood. Like all unicorns he allows only maidens to approach, but those who ride him are turned to stone by the end of the journey, and serve the beast forever more. His destruction is presumed to be the prerequisite for ending the curse.
—Inner Sea Bestiary 37
I should have mentioned yesterday: No radio show to post this week, as I was hanging out in Boston on Saturday.