The water continued to lift in heavy beads, and they grew thicker and more gelatinous the more the creature used his magicka. If the attempts had been successful he might've reversed the effects - but as it stood now, a few inches of the river had already depleted and been absorbed in to the storm. Amras would need to fix this mistake before something worse happened! Such as, perhaps, the full absorption of the river into the storm above.
Similar to the attempts before, Amras' magicka took on a life of its own as it was sent forth to harness the water. Rather than causing things to slow down or to stop, the energy continued to force the water together in to thicker and thicker droplets. After this particular dose of magicka the upside-down-rain had become something else. The drops had condensed among one another into tiny rivulets that poured upwards, in to the storm. At this rate the river would be drained in a couple of hours - and then who knows what would happen to the rest of the caves!
Amras was doing a valiant effort of correcting what he'd screwed up. If nothing else, he would have a grand story to tell to future gemlings (if the caves survived the tumult of the storm). His shouting did nothing to remedy the situation, however, by sending his magicka at the stone to create a brilliant display of neon lights, something did appear to shift. The light within the boulder was incredibly bright; the intricacies of the design reflected off of the stony surfaces, casting everything in the vicinity of the river with a violent red glow.
The pattern fluctuated as it picked up on Amras' power, and by drawing his magicka into the boulder, soon enough a brilliance shone from it that may have settled itself permanently within the boulder's cells and atoms. It took quite a lot of magicka to accomplish, but he was an accomplished magician at this point. Although it was unfortunate that his efforts to control the water had been ultimately useless, at least the caves would benefit from a nice year-round beacon.
The storm, however, did not think much about the boulder. The water continued to lift in to the swirling vortex of magicka that coated the ceiling. And then, the water seemed to slow its ascent. It lost its viscosity, becoming less and less like gel until it resembled rain again, and then things began to fall (properly, like rain). A reaching appendage-like structure made of swirling wind, water, magicka, and who knows what else, began to sweep towards the boulder - Amras had done it! He'd garnered the attention of the storm's eye. The river was forgotten.
As the dark vortex shifted towards the boulder, rain fell from its depths. First in fits and starts, then in sheets, until the downpour was drenching the otherwise dry avenue of Polaris. The water settled wherever it wanted to - mindless, empty, as water usually was. If nothing else, Amras had succeeded in redefining the path of the river. Most of it settled back from whence it came, but there was a vast volume of water spreading out like a shallow lake off to one side, and it was moving along the terrain in accordance to gravity, finding a home for itself.
The storm's eye thrashed above the stone until a tendril of force came sweeping down from it; like an array of spider's legs, the storm reached for the boulder and abruptly lifted the object clear from where Amras had found it. The violent tearing of the stone from its settled point was an obnoxious and terrifying sound - and then the vortex shifted around it, widened and contorted, becoming a great pit with swirling energies arcing from point to point, and the boulder was swallowed whole.
While Amras makes his escape, the storm seems to be fixated upon the glowing boulder. The object tumbles and rolls within the grasp of the vortex, its light catching in the gaps between the clouds or carrying on the flashing light that arcs from point to point throughout; there is no telling how long this sentient powerhouse will be fixated upon the object - however, even now, the light with which the boulder is imbibed has begun to flicker and dim.
With or without the boulder, the storm shifts away from the cluster of rocks, looms temporarily over the river, and cascades closer to the spire with every drawn-out moment, until it has dissipated from the area completely.