If you've entered Athron's Lair from the outside without talking to Sulfras you'll have to make your way to the northwest corner and down the ramp to speak to Sulfras. If you have spoken to Sulfras already make your way to where there's a magical barrier blocking entrance to the lair.
The room that the barrier is blocking contains Athron's Drakelings, who will attack you, but whatever you do, don't harm them. There's a teleporter in the southeast corner of the room which leads to Athron.
The easier way to enter is through a secret passage just to the southeast of the barrier, but you'll need Dispel Barrier Lv.2 or a Piercing Crystal and Move Mountains Lv.2 or a Stoneshatter Crystal to get through.
Once you're in Athron's room, speak to her until she tells you that the metal you need is in the middle chest along the southern wall. Don't open any of the other chests or Athron and the Golem guards will become hostile and attack you. I don't know what the result of killing the dragons is, but I don't think it would be a particularly wise thing to do.
Take the metal back to Sulfras if you already have the ritual from Khoth, or go get the ritual from Khoth and then return to Sulfras. Once you have both she'll make Beastslayer for you, which is useful in fighting the Alien Beasts in Footracer.
