After a ferocious attack by Wargs in Hollin, and a close escape from the Watcher-in-the-Water outside the Westgate of Moria, the Fellowship of the Ring takes refuge within the Dwarf-kingdom, where, however, they are confronted by even greater perils. Within the great maze of Moria’s mines, Gandalf drives off Orcs and huge Stone Trolls with lightning flashes from his Wizard’s staff. In this, Tolkien is drawing on a Scandinavian folk tradition that lightning frightens and repels trolls. It is a belief that has its origin in Norse myths in which the god Thor makes war on the frost and stone giants by striking them with his thunderbolt, the “Hammer of Thor”.
And yet, Orcs and Stone Trolls, however numerous, are by no means the greatest threat in the mines of Moria. And even Gandalf’s power is sorely tested to keep the Fellowship safe from “Durin’s Bane”, the terror that, over a thousand years before, drove has driven the Dwarves from their ancient kingdom of Khazad-dûm. As we have seen, Tolkien’s source of inspiration for this monster was the fire giants of Muspelheim, the Norse subterranean “region of fire”. This was one of the mighty Balrogs of Morgoth of the First Age that survived the War of Wrath. For millennia, the Balrog hid itself deep beneath the Misty Mountains, until, by chance or fate, it was awoken by the deep-delving Dwarves of Khazad-dûm.
In Norse myth, we hear that, on the border of Muspelheim, there crouched a giant guardian who was armed with a great sword of flame. Early Christians saw this guardian of the gates of Muspelheim – known as Surt, lord of the fire giants – as the Satanic antithesis to the biblical Archangel Michael, with his righteous sword of flame. However, the battle on the Bridge of Khazad-dûm between Gandalf and the Balrog of Moria in The Lord of the Rings has a specific mythological precedent in the Norse battle on the Rainbow Bridge of Asgard between the god Freya and Surt, which will take place on the last day of Ragnarök.
Both battles begin with a blast of a battle horn. In Tolkien’s tale, Boromir blows the Horn of Gondor, while in the Norse tale the god Heimdall blows Gjall, the Horn of Asgard. Like the Balrog of Moria who fights Gandalf on the Bridge of Khazad-dûm, Surt the Lord of Muspelhiem fights Freya, the god of the sun and rain, on the Rainbow Bridge linking Midgard and Asgard. Tolkien’s Bridge of Khazad-dûm and the Norse Rainbow Bridge both collapse in the conflict, and the combatants in both battles topple into the abyss below. Surt and Freya are entirely destroyed in this battle, while the Balrog and Wizard continue their struggle until the Balrog is slain, although at the cost of Gandalf’s bodily form as the Grey Wizard.