Grand Apothecary Putress

[Spoilers]
The Wrath Gate, the final stand of the Lich King is assaulted by both the Alliance and the Horde, the Lich King's demise is near! The Alliance soldiers yell "For Lordaeron!" as they prepare to avenge their fallen brethren, while the Horde prepare for the glory of battle.

Bolvar Fordragon, paladin and former (Unofficial) leader of Stormwind leads the Alliance soldiers into battle charging head first into the legions of the undead, they appear to be easily winning but the Vrykul come and put up a fight.

Highlord Saurfang (Younger, not Senior) leads the Horde forces into the battle and helps the Alliance slay the Vrykul, he even takes after his father doing the trademarked "Cleave" of his slaying three Vrykul at once.

The fight is finished, the Alliance and Horde appear victor over the Lich King's forces, the Alliance call out Arthas on his betrayals and acts of evil, the gates open and out comes the Lich King wielding Frostmourne, without much discussion after Saurfang assaults Arthas and gets one shot - Arthas then drains his soul.

Right before the going gets good, Arthas and both the Horde + Alliance are distracted by a large explosion in the back, confusion is set upon everybody and then a voice speaks out, that of Putress - he gives a short (but very cool) speech to Arthas and then blows up everybody unlucky to be in the battle.

Bolvar orders the forces to retreat (or they'll die, but that's obvious) and we see glimpses of people melting, Arthas himself is weakened by the plague and he retreats. Bolvar says his final words as he looks around as people are dying, he collapses and coughs before rolling on his back (Presumed dead at this moment, as you hear his death rattle).

The dragons arrive and burn up the field of bodies so they may not rise into the forces of the Scourge, you regain control of your character and it's suggested you participated in the above battle but got away.

Horde Prespective:
You survived but at what cost?
Saurfang is dead, the Forsaken betrayed the Horde - what next?

The dragons place Saurfang's armor infront of you, time to tell his pops and we know he isn't going to happy. After reaching Warsong Hold you find Saurfang there with Garrosh, once you talk with Saurfang he's sad but proud his son died a Warrior and in battle - he mentions how Thrall needs you and opens a portal to Orgrimmar for you.

Upon arrival, caravans filled with Forsaken Refugees enter Orgrimmar, all scared (They should use WOTF) and curious to what's going on, you find out Orgrimmar is now in a state of Martial Law.

--
From Wikipedia:

Martial law is the system of rules that takes effect when the military takes control of the normal administration of justice.

Martial law is sometimes imposed during wars or occupations in the absence of any other civil government. Examples of this form of military rule include Germany and Japan after World War II or the American South during the early stages of Reconstruction. In addition it is used by governments to enforce their rule, for example after a coup d'état (Thailand 2006), when threatened by popular protests (Tiananmen Square protests of 1989), or to crack down on the opposition (Poland 1981). Martial law can also be declared in cases of major natural disasters; however most countries use a different legal construct, such as a "state of emergency".

--

Upon entering Grommash Hold you find Sylvanas and Thrall discussing important matters about what the hell is going on - Thrall explains everything to you:
Putress and his Royal Apothecary sided with Varimathris, they betrayed the Horde and took over the Undercity - it's now under legion and RAS control.

Jaina appears and talks with Thrall trying to keep the peace, Varian is very angry and ready to declare war against the Horde because Bolvar was like a brother to him and was slain because of the Horde, they discuss a little bit and Thrall pretty much says to Jaina to tell Varian "We'll handle it, sit back and relax".

Thrall opens a portal to the Undercity and orders you to go through, upon arrival you find yourself infront of the Undercity being attacked by Vol'jin and countless Horde Siege Vehicles - You, Thrall and Sylvanas are going inside to deal with the traitors.

(Sylvanas starts singing Lament of the Highbourne)

Varimathris stops you everywhere, but the spirits (Guided by Thrall) help you pass his traps until you eventually arrive into the Throneroom where he summons his master, you fight him and stop the summoning and eventually defeat him.

"Lok'tar, Ogar!"

Everything's looking good now, time to go grab Putress and finish this fig-

Loud alliance horns shake through the Undercity, Varian arrives with an Alliance army and says that he's going to kill Thrall, but Jaina arrives and before letting it go any further out of hand she freezes the entire army of both alliance and horde and teleports herself and the Alliance army back to Stormwind.

A portal to Orgrimmar is opened, the fight is ended but the fourth war has begun.

--
Alliance prespective:
What in the light just happened?
The Lich King's defeat was within grasp! What happened!

The dragons lay Bolvar Fordragon's shield infront of you, the sheer horror of the world is suddenly thrust upon you. The Dragon queen tells you that you must tell Varian Wyrnn and important message, he'll no doubt be angered but the dragons tell you:

"All is not lost. From the ashes of the fallen will rise a force that will unite nations and purge the evil from this world."

He mustn't lose faith. Go now, <name>. Your people need a hero. They need you.

You wander into the the Throne Room of Stormwind, horrified of what you just experienced and you give the Shield to Varian, his anger / rage is obvious and you know bad things are about to happen for both the Horde and the Alliance. Jaina Proudmoore opens a portal to Orgrimmar, Varian orders you and Jaina to go to Orgrimmar and find out what in the light is going on.

Upon arrival you find yourself in the middle of Orgrimmar's Grommash Hold, Thrall and Sylvanas are discussing important matters when suddenly you and Jaina interrupt the discussion - Thrall tells you that the Horde had nothing to do with the Wrath Gate and he'll deal with it, but if provoked he will fight back. You have free roam of Orgrimmar and can do what you like, but to further the quest you need to go into the Stormwind Portal and leave back and give the grim news to King Varian.

King Varian doesn't listen to reason, he sent alliance armies to the Undercity even before you were sent into Orgrimmar on the diplomatic mission, the fool! A portal to the Undercity is opened, it's time for good ol' fashioned manhunt, Varian and Jaina task you with heading into the Undercity and avenging Bolvar by slaying Putress, something everybody can agree on.

(Continued below)

When first glancing Putress, I am immediately reminded of the 'God of Death' from the game GuildWars, named Grenth.

An image so you can see what I mean...

http://guildwars.wikia.com/wiki/Image:Avatar_of_Grenth_concept_art.jpg

I'm not saying it to go "Oh, Blizzard ripped off ArenaNet", quite the contrary... I find it a very fitting tribute and as they say, imitation is the best form of flattery. Just cross your fingers to hope they don't re-use the model endlessly. <_<;;

Either way, this is the man in charge of the Royal Apothecary Society it seems, and believe me, the name is going to be incredibly important for all players to remember -- especially Horde players, who get to ... welll.... let's just say it's an incredibly epic spoiler. But if you're interested in seeing what Putress will be responsible for, follow this link (blizzplanet.com). But I cannot impress on you how incredibly epic this spoiler is. As in, it changes the entire face of the Horde and the Horde/Alliance dynamic.

I will personally recommend that it is worth rolling an opposite-faction alt just to experience this event from both Horde and Alliance perspectives, to see Putress' full "legacy".

edit: thank you Suzaku, I didn't realize there was an alliance side to this! I should go digging to see if someone filmed the quest chain from their perspective. =)

edit 2: As of the evening of October 26th, 2008, Grand Apothecary Putress has spawned in the city of Shattrath by the base of the Aldor teir. He stands there with several of his Apothecary Researchers, busily working on the cure of the Plague currently decimating Horde and Alliance cities. Horde players have quests associated with him in assisting with the research/dissipating information concerning it (I really don't know, I don't have a Horde alt high enough level to find out).

Fun stuff!

Undead Monsters and Demons hinder the path to the Apothecary, the Alliance are defeating every enemy from the Sewers and more - you stumble upon a dead squadron of dead Horde soldiers but shrug it off and head further into the bowls of the once-proud Lordaeron. Putress starts freaking out, he knows the Alliance are here for his head and everything he worked for is in ruin - the enemy forces try to overwhelm you and the Alliance, but with the combined forces you finally enter the Apothecary and there stands Putress.

His end draws near, end Putress and Bolvar will have been avenged! This is the end!

King Varian Wrynn yells: And justice is served!

The Alliance is victorious, the bastard Putress has been slain! Now we need to deal with Varima-

Thrall's orcish yells are heard from the throne room, there he stands with Sylvanas and heroes of the Horde victorious over Varimathras when you and your king barge in (Jaina remained behind, she won't deal with seeing Thrall), Varian orders the fight to be finished now - once and for all and just before the clash of forces happen - Jaina appears and freezes both armies, she teleports the Alliance forces to Stormwind.

Upon arrival in Stormwind, King Varian tells you to go conquer Northrend for the Alliance. Putress has been slain, but his legacy remains - the fourth war has begun.

Conclusion:
Once you arrive to Northrend, Alliance and Horde aren't fighting side by side but are fighting each other as the Lich King destroys them both and raises them into undeath, all neutral factions /facepalm as the world's fate is being gambled by this pointless war.

EDIT: Alliance version completed, and thank you Avandas but i'll not update the information because your info is pretty much spot on. :D