The Great Masquerade quest chain

The Great Masquerade was the alliance quest chain that leads to obtaining the Drakefire Amulet, the key to Onyxia's Lair. This was one of the most arduous quest chains in the game, involving multiple trips into Blackrock Depths, a major event in Stormwind City, and a raid in Upper Blackrock Spire. It could require Lower Blackrock Spire runs as well, to acquire the key to the raid area.

The Great Masquerade
Monumental events, from such simple beginnings...

Prelude: The Dragonkin Menace
Morgan's Vigil struggles to survive against the pressure of the Black Flight. Helendis Riverhorn asks you for help pushing back their forces.
 * Dragonkin Menace (quest)

Showing sympathy for the people of Morgan's Vigil, you combat the Black Flight's forces, slaying a great many of them, including a fearsome Black Drake.

As have other people elsewhere on Azeroth, Helendis has other problems, and used this task to see if you would be up to challenges greater yet...

Act 1: The True Masters
Helendis tells you of the outpost's findings: that they believe the Blackrock orcs are under the control of the black dragonflight. Helendis has decided to "kick the issue upstairs", and wants you to take a letter to Magistrate Solomon, in Lakeshire, in the Redridge Mountains.
 * The True Masters

Solomon opens the letter, and decides that Stormwind must respond, or all is lost. He directs you to Highlord Bolvar Fordragon, in Stormwind Keep.
 * The True Masters (2)

Bolvar, though, is reluctant to send troops without having undisputable proof. (You may have learned earlier, that it's hard all over, troops are spread thin, and nobody is getting enough military aid... See the '' quest chain.)
 * The True Masters (3)

Bolvar asks you to speak to Lady Prestor, who downplays the situation.

Politician that he is, Bolvar determines to make you an acting deputy of Stormwind, and sends you back to Magistrate Solomon.
 * The True Masters (4)

Understandably, Solomon is not overjoyed to find that instead of an army, he only gets you...

As deputy of Stormwind, Solomon says, you are required to report to Marshal Maxwell, back at Morgan's Vigil.
 * The True Masters (5)

When you get there, Maxwell just laughs.

It seems you aren't the first to be so deputized. Brave men and true have been lost in this fight.
 * The True Masters (6)

The former commander, Marshal Windsor, had gathered a great amount of information before being ambushed and taken by the orcs. The only person to win free of the fight was Ragged John, who has retreated to a cave to the north.

You travel north to Flame Crest, and locate Ragged John, and tease the story out of him. It seems that the orcs failed their assault, and instead the Dark Iron dwarves captured Marshal Windsor alive!

Act 2: The Search for Marshal Windsor
Marshal Maxwell directs you personally to go into the Blackrock Depths and find Windsor.
 * Marshal Windsor (quest)

You gather a small group of adventurers, and venture into the depths. You manage to defeat a number of the Anvilrage guards, including an interrogator who has the key to Windsor's prison cell.

Marshal Windsor is furious with Bolvar. (Join the club, mate. They've got truncheons and inscribed breastplates...)  But without his notes, and without Ironfoe (his mace), Windsor is despondent. The situation appears hopeless.
 * Abandoned Hope

You return to Maxwell, who believes that Windsor has simply gone around the bend. Still, he rewards you for your dangerous work.

Unwilling to completely abandon Marshal Winsor to his fate, you travel back to the depths, and go ... investigating.
 * A Crumpled Up Note (quest)

On one of the bodies, you discover The note mentions a couple of high ranking dwarves among the Anvilrage - General Angerforge, and Golem Lord Argelmach.

You take the note to Marshal Windsor, who believes that between them, these two Dark Iron dwarven leaders hold the most of his notes. If you retrieve them, it will be enough to force the issue in Stormwind...
 * A Shred of Hope

You and your friends venture into the dark places of Blackrock Depths and overcome both the general and the golem lord, retrieving Windsor's plans.

Marshal Windsor seems completely re-energized by the return of the tablets. He insists on leaving the dungeon immediately, and asks your aid in escaping.
 * Jail Break!

First, however, there's some unfinished business that he has to attend to, other members of the patrol he was with, fellow prisoners.

You escort him to a supply closet, where he rearms himself. He may not have Ironfoe with him, but at least he's got good solid steel between him and the world. He leads you across the prison compound to the other cells, where certain people he sets free, and others - treacherous ones - he dispatches rough justice upon.

Eventually, though, you manage your way back out of the depths. Once in the clear, though, even you can't keep up with him. You make your way back to Morgan's Vigil, and talk with Marshal Maxwell. By the time you get there, Windsor has been there and gone again, off to Stormwind.

Act 3: Revelation at Stormwind Keep
Maxwell tells you that Windsor's instructions are for you to meet him at the gates of Stormwind, with as many people as you can gather. (You do recall that Windsor was the post's commander, right? Maxwell was merely standing in for him in absence of direction from the Keep...)
 * Stormwind Rendezvous

You gather such a force as you are able, and head to Stormwind.

You meet up with Windsor at the gates of Stormwind, resplendent in polished armor, white charger and all. The guard at the gate challenges him, and Lady Prestor calls for his head.
 * The Great Masquerade

Bolvar countermands her, though, commanding that none of the guards are to touch him.

You escort Windsor through the city to the keep, where he presents his information to the highlord. The highlord is stirred to action, yes, but it is too late for Reginald Windsor - Lady Prestor reveals her true identity as the broodmother Onyxia, slaying the hero and summoning a good portion of the black dragonflight to wreak havoc.

Windsor's act of defiance has broken Onyxia's hold on Bolvar, though, and he makes up for lost time, slaying many of the black dragonflight (with your aid), and forcing Onyxia to retreat.

Act 4: The Drakefire Amulet
Breaking Bolvar's Medallion freed him from Onyxia's control. The amulet also gave him some access to Onyxia's mind, though. With the amulet, you could penetrate the defenses around Onyxia's Lair, and perhaps put an end to her.
 * The Dragon's Eye (quest)

But the medallion is shattered, and must be mended if that is to be attempted. While he can't direct you to anyone specific, he can tell you that another of dragonkind might be able to help you rekindle its powers.

You search the world, and after much travail, find yourself in Winterspring, in the presence of the Matron Protectorate of the blue dragonflight, Haleh.

Haleh tells you that the amulet is one of Onyxia's scales, enchanted and transformed. Useless now, she says, but repairable. To repair it, you have to get the blood of a black dragon champion. Haleh directs you to one - General Drakkisath, ruler of the dragonspawn army of Nefarian.
 * Drakefire Amulet (quest)

You gather an army, and assault Blackrock Spire, beating back the best the black dragonflight can throw at you. You defeat Rend Blackhand and his mount Gyth, and the chromatic dragonflight that Gyth is part of. And finally, you face and slay the black dragonflight's general himself.

You return to Haleh with a vial of his blood, and watch while she repairs the amulet, restoring its enchantment and effectiveness against Onyxia's wards.

As you leave with the amulet, she wishes you good luck on behalf of the blue dragonflight.

Rewards
This permits entry into Onyxia's Lair. Don't lose it!

Reputation awards from this chain:
 * about 1085 Darnassus
 * 2850 Stormwind
 * about 685 with other Alliance factions