The Great Glacier

So much about the Great Glacier is unknown. Most of the details of its existence are merely bits of legends or myths taken from the Ulutiun people's history. According to their oral history, handed down to each generation, the Great Glacier was created at some point between -3000 DR and -2000 DR when the elemental god Ulutiu laid himself to rest on barge made of axiomatic ice in the Cold Ocean, a favorite inland sea creation of his. The barge sank soon after and the Necklace of Ulutiu (an artifact that he wore and a holy item that the Ulutiun people say could still be found) encased his body in ice when his divinity had departed to the Astral Plane.
The Cold Ocean became completely frozen by the necklace's magic over the next century, then due to some type of interference from the Giant kingdom of Ostoria (or variously from the work of evil White Dragons, or sometimes due to rituals perpetrated by wicked Frost-Fey) the glacier grew and encroached upon the land as well. Eventually, the ice completely destroyed Ostoria but was held in check by the high magic of the Silver Elves of Lethyr (who once dwelled in what is present day Rawlinswood, before it was transformed into a fell place).
Over three thousand years later, the Ice Queen Iyraclea was granted the power to overcome their high magics by her God, Auril. The glacier began to grow larger once more, at one point coming as far down as the Galenas and into The Ride, Thar, Vaasa, Damara and even Narfell. However, another tale credits the gold dragon Protanthyer the aggressive expansion of the glacier, as one of his plans to get rid of some type of festering evil from Vaasa. Although there was no absolute proof of this, given Protanthyer's outstanding mastery of the arcane, such a feat was not impossible for him, giving credence to this version of history.
It is not known exactly why the growth of the ice body stopped, but it is known that it did begin to retreat in the Year of Spreading Spring 1038 DR over 300 years ago, suddenly clearing massive swathes of formerly frozen land on its southern edge and releasing The Ride, Vaasa and Damara from the clutches of an endless winter. The Great Glacier has continued its retreat, but the pace has slowed to a crawl and none by the Ulutiun people notice.
At the Edge of the Ice
The Ice Run caves have been exposed in the last 2 or 3 decades as the glacier continues its slow motion retreat. These caves go so deep into the glacier that it is said you can find a passage way to the ruins of ancient Ostoria, the Palace of the Ice Queen, the vault that contains the Necklace of Ulutiu, the lair of Protanthyer, or even more incredible finds. Perhaps nothing can be found down there, and as of yet, no adventurers have made the expedition (or at least, none have come back).