I Choose You, Runemaster Molgeim (10 player)

A reference to Pokemon of course.

Killing a boss of the Iron Council Supercharges the remaining bosses, healing them to full, increasing their damage and giving them new abilities. To get this achievement, Runemaster Molgeim must be killed last, which is considered the first tier of hard mode.

Molgeim starts off with the Runic Barrier and Rune of Power abilities.
When 1 other boss is killed, he can cast Rune of Death, a void zone.
When both other bosses are killed, he can create a Rune of Summoning, which in turn summons suicidal Lightning Elementals, exploding with Lightning Blast.

We attempted this on July 2, 2010, with only the knowledge of what each of the bosses did per supercharge. After some failures and sobbing tears, we finally pulled through! The following is how we did it.

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Ulduar 10-man, Assembly of Iron order - Steelbreaker, Stormcaller Brundir and finally Runemaster Molgeim.

Group: 4 Paladins (2 tanks, 1 heals, 1 dps), 1 Boomkin druid, 1 Blood Death Knight (dps until Cata), 2 Priests (1 Disc heals, 1 Shadow dps), 1 Warrior and a Destruction Warlock.

All of the regular buffs put out, including the Fish Feast food buff and the warrior's shout. With me being Main Tank, this fight is pretty easy with coordination.

Firstly, mark your targets. Have the off-tank run and grab aggro of the 3 bosses and hold them in the back, around where they start. The OT's job is to keep them occupied while avoiding Brundir's Overload and keeping them both out of Molgeim's Rune of Power.

The MT will go up and pull Steelbreaker from the batch as the OT starts the event. MT should pull Steelbreaker back to the circle by the door you came in from. From here, all dps should be focusing on Steelbreaker. MT will have to watch for Runes of Power and be sure to keep Steelbreaker out of them while also paying attention to Fusion Punch because if it is not dispelled ASAP, MT will certainly die. Paladins make great tanks for this part because they can cast Cleanse and will remove the debuff without stalling a healer's cast.

Once Steelbreaker falls, the other two gain a Supercharge. Brundir will now use Lightning Whirl and Molgeim will now also use Rune of Death. MT should go to the back where the OT is dancing with the two others and pull Brundir where they had Steelbreaker. Lightning Whirl can be healed through and isn't a major concern, however, with all dps focusing on Brundir now, the Overload is a big concern. Be sure to move away at least 20 yards before it kills half your party and makes you say naughty words.

The other, equally important, thing to watch out for is the Rune of Death. This looks similar to a green Death and Decay and inflicts massive damage to everyone who stands in them. Avoiding these things is relatively easy if you have a DK with Death Grip or a Paladin who can use their shield and silence Brundir. (Being that he is a caster, moving him may be a pain >.< )

Once Brundir dies, Molgeim gains a second Supercharge. This final step comes with Rune of Summoning. These little runes look like small, red pillars of light and spawn 4-6 little air elemental things. These can swarm a tank and kill 'em very quickly, so the MT or OT (whoever keeps Molgeim) needs to kite away from the Runes of Summoning and avoid the Runes of Death. ...Did I mention also keeping him out of the Runes of Power?

The little air dudes will explode upon reaching the boss, NOT the raid. This means melee, YES you CAN attack them.

For whichever tank keeps the boss, this part will be the hardest. AoE damage is key for the little air dudes and situational awareness is of the utmost importance. With luck, the raid will drop Molgeim and grab this achivement, snag a quest item to unlock the last boss, Algalon, go home happy and drink some fine ale!

Best of luck to you all and I hope this helps!

...on a side note, if you happen to have one of those little Iron Boot Flasks before you kill Molgeim, you'll also get this achievement for your efforts! Please note you do NOT have to have the flask on for the ENTIRE fight! So long as you use the flask before Molgeim dies, you'll get this since this is considered an event. :)

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Edit: Fixed a few spelling errors and grammatical curiousities...

UPDATE: As far as the PTR goes for patch 4.0.1, a couple changes will take effect. One, paladin tanks will no longer be able to cure their own magic effects; this is especially a headache for Steelbreaker. This brings us to number two: be sure on this fight to have either a paladin or a priest healer on the tank taking Steelbreaker, as they will still be able to dispell magic. Shamans and druids cannot.

UPDATE: As of 12Oct10 (the release of patch 4.0.1), It's official; tank and dps paladins can no longer cure magic effects. Before you attempt this, you will need to verify that this ability is available from at least one of your healers and also verify that your tank has a healthy chunk of health before attempting this. Fusion Punches really hurt!

UPDATE: Completed this again on 8Jan11, as we push through for hard modes with lower level guild members. This fight has become alot easier, now that the majority of the run was filled with level 85 toons, but the mechanics still should be heeded. The fusion punches still hurt, but if they are not dispelled right away, it probably won't kill a tank. ...least for a little while. The little air dudes still suck, but with all of the new toys given to players in the 80+ levels, these should be cake. All in all, I hope that this guide has given some insight to those who would seek it and I would love to see posts on those who have employed this technique and their reactions. Still haven't made a video yet of this strategy (because I keep forgetting to), but I will update this once more with a link once I have it made.