The first region of this zone includes the Deep Forge itself (to the west), a number of mobs, and a central named in front of a joint lava-fall which features five symbolic glyphs as part of the magical language featured on architecture throughout Lavastorm. Note the order of these five symbols and keep them for future reference.
After clearing the first area, head to the Deep Forge. (There is a book here, On Summoning a Greater Fire Elemental, gives quest Something Greater.) To be able to kill The Doomsmith, be sure to kill all the automated hammers during the fight to prevent the AoE he casts. In order to open the lava-fall, the group must right click the correct symbol on the five crystal symbol pillars in the Deep Forge room. Each will light up if they are triggered in order and then the lava-fall will open, which leads to the Magmaborn Furnaces. Clicking the incorrect symbol will cause the sequence to start over with the first symbol again. From the door, the sequence is Far Back Left, Near Right Side, near Right Front, Near Left Front, Far Right Back - or if you loosely translate the symbols to alphabetical characters "UM3YE".
Proceed in to the room past the Lava Fall. This is a challenging room. There are two circular valves on either side of the room (east and west) flanked by two triple-ups.
Prior to the turning of these valves, the single-ups on the floor below will attack whomever enters the Magmaborn Furnaces one after another on a timed basis, one every thirty seconds. You could have a mezzer watch for the mobs sprinting up the ramp and have them rooted/mezzed until you have the valves turned. Please note that as each single-up is killed, it is replaced by a triple-up formed on the grate floor below. Therefore, it is imperative that the two valves be turned as soon as humanly possible. When you do turn both valves, the room will flood. If you speak Krombral, the dialogue will be hilarious as all of the mobs on the lower grate level are destroyed by flowing magma, leaving only the named Firelord Kaern and the Deep Forge footman patrols.
At the back of this room, to the west of Kaern, is Najena's Treasure, which is openable using Najena's Key. When approached, a message will say "the chest glows as you approach it." This is the Void Shard chest.
When you engage Firelord Kaern the lava-fall will close, preventing anyone from reviving and rejoining the attack should you engage him and a member of your party die. He is fairly easy to defeat provided you are careful. Slowly walk the mob around the zone in a clockwise route, and remember you have to kill him before he gets back to where he started. Once every 20 seconds he will spawn a Lava Pool around his current target which deals around 3000 damage every 4 seconds. It is incurable so don't stand still too long! High DPS and constant movement will be the path to glory here. In addition, once every three minutes he teleports the player furthest away from him into the middle of the lava. Lucky for casters, you can still hit him with spells. Simply run back up the platform and rejoin the fight.