So, you're inside. Welcome to hell =) First it seems easy, but then gets much tougher closer to the bottom. Anyway, start buffing. Buff your armor with Bludgeon and Fire Banes (and Impenetrability of course), and I strongly suggest to buff your Underwear with Impenetrability and Bludgeon Bane as well. As for Life Protections, I suggest casting Armor, Bludgeon, and all Elemental Protections. You will almost certainly receive debuffs through the dungeon - Life/War Inept, Imperil, Bludgeon, Lightning, and Flame Vulns. So make sure that you're ready for those.

You will meet Diamonds Golems, Vapor Golems, Wisps, and Fire Elementals close to the top. Run through the liquid-magma hallways as quickly as you can to avoid damage. When you finally get to a gap with a bridge on the left (right pic), jump over the gap - do NOT take bridge. If you do, you'll be ambushed by Hellfires. So, just jump over:

Keep fighting - Mages Imperil, Melees and Archers kill. Cooperation is a must. Make sure to keep alive the person who has the Bellows. Keep a Healer's Heart handy - very helpful!

When you reach the point in the right picture above, you must split into two teams. One team must travel down deep into hell, while the other team must hold a room with levers. Cooperation and communication is EXTREMELY important in this part. I have been on both teams. The team travelling down into hell is in for a treat - many many Plasmas, Vapors, Hellfires, etc. In the left picture below, you see a big room. In the back of this room you will find the Sluice Bar. Use the [ and ] keys to find it. Make sure someone constantly heals the person grabbing the Bar. In the right picture, you can see us getting slaughtered. Combined effect of lag and the Plasmas' respawn prepared us the grave. I actually did not die, hehe. I managed to do a Stamina-to-Health, fight a bit more, and then recall - resistance was futile. The bastard kept resisting my Imperil, so the only left person in there (Rhal - Staffer) wasn't hitting him for much.

During the second trip, I was on the lever "team." The team consisted of: Etrel. Actually it was really easy, because the Plasmas were lured away from the lever room, so I just had to stay buffed, hit the levers when needed, and get ready to get the hell out of there when the deed was complete.

In the picture above on the right, you can see the message broadcasted when the Bellows are handed in. Once that happened, the group below had to quickly run back up through the doors that the levers open. Then they hit the Surface portal. Now it was my turn to get out - a little jump off the bridge into some hot lava, some phat Diamond-spell evasion skills, and I was free =)

At this point in time, my favorite create in Dereth spawns - the Behemoth of Tenkarrdun. So, out of the Foundry, and on to Caldera we go!