In the entry on ourdivars, Bestiary 6 states:
Ourdivars are spontaneously formed when called forth via spells like lesser planar ally. They toil at the behest of their conjurer creators, acting as tools of chaos across the planes.
This is suuuuuper interesting to me. The creature-spontaneously-created-in-the-act-of-conjuration is a common trope of fantasy fiction. But in fantasy gaming, we tend to assume all outsiders come from a specific somewhere—after all, our characters can visit those planes. Even summoners, who call into being conjured creatures the way most people conjure up chili fries, supposedly get the spirits they call from…someplace. That makes an outsider brought into existence purely in the moment of conjuration an interesting beast indeed.
Now give it the body of a crystal lamia, with a weapon hand that can morph from spear to saber to morning star with just an effort of will (as if they were Junkions in Act 2 of The Transformers: The Movie!)…well, that’s a monster worth conjuring/creating.
But once they're created, how do they react? As living embodiments of chaos, following orders to the letter isn't going to be a strong suit, even in the service of a chaotic caster. Are they thrilled at their sudden coming-into-being, or do they seek to return to the Maelstrom, à la Mr. Meeseeks (“Existence is pain!”)? That leaves a lot of room to play for an inventive GM and a chaos-loving conjurer.
The enemies of Mortis Minelus have all wound up dead. But each time, the method has been different—beaten to death, bludgeoned, pierced, slashed, even warped by some form of raw magic. Minelus himself wears the purple and blue robes of the pacifist Morning Glory sect, having sworn “to raise no weapon, nor fire a spell in anger”—and spells testing his veracity have returned nothing incriminating. The truth is that Mortis Minelus is an accomplished conjurer, using called ourdivars to do his wicked work.
Debtors know they can always find refuge in the Abbey of Alms. First, the land the abbey sits upon is properly part of the March of Lady Weatherall, and thus not within the jurisdiction of the Lord-Mayor or his Dunners. Second and more importantly, the constantly shifting stained glass window in the ramshackle abbey calls ourdivars to fend off any scion of law—be they archons, devils, paladins, or even humble local watchmen trying to fulfill a writ of collection.
Lamias and spirit nagas sometimes summon ourdivars for coitus, not combat. The resulting entropic creatures are inventively deadly and hate the trappings of humanoid civilization even more than their serpentine mothers.
—Pathfinder Bestiary 6 213
Do I get to say I’m the authority on nagas? Yeah, I’m gonna say it.