Movanic devas serve in the infantries of the various angelic armies, as the Bestiary 2 notes. That’s also why they guard the Positive and Negative Planes—where relations with the insular and disagreeable inhabitants don’t require the political finesse or stoic might of the monadic devas—and the Material Plane—where their numbers are needed to watch over the many different peoples and their souls.
As with most angels, movanic devas are far more likely to help PCs than hinder them, especially as summoned allies. But there are still reasons to throw them in the PCs’ path if you want them to throw down…
Carsiel has been loaned out from his detachment to the house of a fey lord—a thank-you for a service the fey rendered a planetar colonel. The fey is amused to have Carsiel stationed in the deadly hedge maze that he forces particularly insufferable mortals to navigate. The movanic deva will do what he can to help good-hearted adventurers; aside from his arsenal of benevolent magicks, his nature’s pacifism ability is particularly useful for soothing the many aggressive animals in the maze. But if they try to enter the garden he guards, they will still be met by his +1 flaming greatsword.
Psychopomps have spirited away an important soul a movanic deva was supposed to receive. Instead, he encounters an adventuring party whose divine caster happens to serve the same deity as the psychopomps (or at least, as the psychopomps claimed to serve). Suspecting the mortals of collusion, he attacks. If the adventurers can calm him down enough to explain the situation, they will discover the soul is of interest to them, too. Aiding the angel will take them to the brilliant cities of the jyoti, with flights of rogue psychopomps and sceaduinar harassing them along the way.
Movanic devas have a special loathing for devourers, who are twice damned—corrupted by the foul negative energy of undeath warped by exposure to places beyond even the Outer Planes. After a Heavenly court charges an adventuring party with planar crimes, the court’s movanic deva prosecutor offers a plea bargain: aid her in tracking down a particularly foul devourer or face her in one-on-one combat.
—Pathfinder Bestiary 2 28
I can’t find any definition for “movanic” anywhere…a made-up word perhaps? The closest I could find was “movant,” which inspired the third seed.
I haven’t talked about the art in the Bestiaries much lately, but Kekai Kotaki’s movanic deva is really sweet.