Board Thread:Lore Discussion/@comment-24358443-20140124004851/@comment-10207438-20140124223737

"Finally, word reached him of Ysgramor and his Companions, newly-arrived from Atmora. For three days and nights, he rode north, and met them as they made landfall on the icy coast near the ruins of Saarthal, which the elves had fortified against them. He offered the Companions his service, and all he had produced in his years of labor. And with Atmoran steel imbued with his enchantments, the elves fell before them, and at last he had his revenge."

- Ahzidal’s Descent

To me it sounds like he enchanted their weapons.