Bergelmir is the last of the Frost Jotun tricksters. His strength lies in the magicks he channels to bring about the destruction of the Nine Realms. His magick comes from the number of Frost Jotuns that he has created, which were not many at the time of the Great Rebirth after Ragnarok. As such, he has not been seen of or heard from in the last millennium, but he has a plan to bring back his race and take over the Nine Realms.
He is scheming something that will destroy the Favoured and their benefactors, and make the Asgardians pay for all they have done to the Frost Jotuns.