Saurtr is one of the two bosses whom dwell within the Pyramid in the Duskin Desert. This boss was the most difficult of the two due to its vast damage output along with its constant ranged attacks. Saurtr is summoned using the Pyramid Amethyst at the bottom floor of the Pyramid on the puzzle frame on the north wall, the same location at which you summon Typhon.

Thanks to Benjo for confirmation of his drops.