The Destiny Of Shia

Once upon a time, there was a wolf that troubling the Gods, Fenrir. The gods then decided to chain Fenrir in the bottom of the world. Now the chains that bound Fenrir weakened because the death of the Elf that guards it. What is the relationship of it all with Shia? Why there is a giant wolf named Salvar who seek her? Did Fenrir successfully break up free and destroy the world?