Board Thread:Lore Discussion/@comment-7153552-20130708162914/@comment-5424581-20130910062222

SajuukKhar wrote: Given that Snow-Throat was, at least according to The Book of The Dragonborn, rendered kingless and bleeding, implying it was deactivated, and that this had to happen before Alduin returned, the stone being anything we see in-game is unlikely.

Alduin and the dragons only returned after it was deactivated. The Eye of Magnus and The Skyforge have, to our knowledge, not changed in recent times. The Thu'um hadn't been largely used in ages. Making all of them being the stone unlikely.

The stone most likely would have been something related to the High King, perhaps one of the jewels on his crown, which could have been cracked or destroyed when Ulfric shouted him down during the battle.

PsijicThief wrote:  In Morrowind we destroy the stone The Heart of Lorkhan was not destoryed, only freed from the enhantments placed on it by the Dwemer.

This is mentioned in both the Plan to defeat Daogth-Ur

"The plan is to permanently disrupt Kagrenac's enchantments upon the Heart, severing connections with Dagoth Ur and ourselves, and rendering us all once again mortal." The Nerevarine will not be taught the secret rituals required to perform the third step. Instead, The Nerevarine will strike the Heart with Keening for a second time, causing its tones to diverge into unstable patterns of interference. Further repeated strikes with Keening will further disrupt the tones, with the ultimate result of shattering and dispelling Kagrenac's original enchantments binding the Heart, thereby severing the Heart's links with Dagoth Ur, and with any surviving Heartwights, and with the Tribunal. Destroying Kagrenac's enchantments on the Heart will also stop the corrupt effusion of the Heart's divine power, and end the Blight on Morrowind. "Dagoth Ur will not expect you to destroy Kagrenac's enchantments on the Heart." No mention of direct destruction of the heart is made, and Azura even mentions it is now free in the ending cutscene for Morrowind, making no mention of it being destroyed.

Not to mention It's impossible to destroy the heart, for it is the heart of the world, one was made to satisfy the other. maybe...the stone was the high king himself?!