In this quest, you're sent to the Ata'mal Terrace in Shadowmoon Valley, to gather Ata'mal Armaments. This metal was once used by the Draenei living in Karabor, but has since been taken by the Fel Orcs, corrupted, and abused. The anvil you just helped Hauthaa make has been blessed by the SSO's clerics, and just happens to be capable of purifying that metal.
So what you do it gather up five of those armaments, then head back to the Isle of Quel'Danas. Stand near Smith Hauthaa's anvil just outside of the Armory, and use the Armaments. This will cleanse them and break them down, making Cleansed Ata'mal Metal.
On the Ata'mal Terrace, the Armaments drop from any of the fel orcs there. The Shadowmoon Chosen, Shadowmoon Slayers, and Shadowmoon Darkweavers. These mobs aren't especially difficult, we've been killing them since the Burning Crusade launched. Nothing scary about them. The only thing to worry about are the Shadowsworn Drakonids, the wandering elite... drakonids. They're not as unforgiving as their Netherwing Ledge counterparts, but can still be a thorn in your side.
This is the final quest in phase 3 of the retaking of Quel'Danas. Its rewards reflect that and are a step up from all of the others. Not only do you get 18 gold, 28 silver, and 350 Shattered Son Offensive Reputation, you also get a choice between two neat weapon oils. Physical DPS can choose the Righteous Weapon Coating, and casters can choose the Blessed Weapon Coating.
As always, for more information on this quest, you can always check out Wowwiki or Wowhead.