Nivibu'rae

Nivibu'rae is a powerful demon, sealed away by magic lost to time by the Nobel Knight, Lady Tiff and the order of Icewind. They are trapped beneath the earth in the centre of Coldkeep under a large, intricately engraved iron plate. They scream, and rage, and curse all who trapped them and all who dare live in the keep's walls.
It is said that Nivibu'rae had large horns like a ram, tipped with icicles. That their skin was tinted blue, and their tail could stab through solid rock. The demon's powers were great, plunging anywhere they went into a permanent winter. Killing crops and freezing anyone who stood in their way. They would use their power to hoard flames away from humans, only giving out warmth to those loyal to them, and were merciless when taking it away.
Riverstoke was a town under Nivibu'rae's dominion, the river nearby barely running as it was frozen solid. Of course many had fought and many had become little more than ice sculptures to line the streets of the town as a reminder. In secret, some brave townsfolk still tried to fight back. Researching the demon, making deals with lesser imps and devils for knowledge, flattering and playing along with whatever games the demon wanted so that they may learn more. When they did, they sent the information far away to the town of Castlewell where a small order of knights with fire in their hearts were working to put the pieces together to finally rid the world of this evil.
After years of work, they had done it. Together, the townsfolk and the order had found a way to trap the demon, binding it to the mortal plane and sapping them of their power. This magic came at a great cost however, Lady Tiff, the best warrior in the order's ranks, was to be bait. She was to be infused with the powers of flame itself, granted only through making many deals with rival demons, and she would be sacrificed to keep Nivibu'rae sealed.
The plan was simple after Tiff had acquired her power, her and the knights would flaunt what they had gained, driving the demon into a rage and luring them out to fight her. While they fought, the mages of the order would cast a grand rite to vanquish the demon and doom their friend.
It went off without a hitch. It is said that the moment Lady Tiff began to use her new powers Nivibu'rae sensed it and let out a great scream in anger. Charging through forest and mountain, freezing all in their path to reach her. The battle was great, lasting days without pause, as they focused on nothing but one another. The Mages chanted and called forth all the power they could muster, each falling to exhaustion one by one. As the last mage used up their strength, Lady Tiff manage to swipe at the Great demon, cutting into their chest and as the blood hit the ground, finished the last of the ritual. The ground opened up, swallowing both Nivibu'rae and Lady Tiff as the immovable seal formed over them, trapping them both forever.
While the knights had saved the world at large, It was too late for Riverstoke. The demon's rage had reduced to nothing more than a frozen wasteland, not a strand of grass still living. To this day, a cold chill carries on the breeze through its ruins.