Chapter II: Wrathion's War

"Prove Alliance superiority to Wrathion"
after 20 losses and a win in silvershard mines, it's not a great superiority...

This achievement is part of the Landfall storyline, and requires participation in Krasarang Wilds.

Before you start these quests, you must have completed the Legendary quest line before it that ended with Breath of the Black Prince. After that you receive Incoming..., and the new quests begin:

The quest A Test of Valor, offered after completion of Breath of the Black Prince, is a side quest of sorts, awarding A Test of Valor as a result.
Incoming...-an optional quest that requires the completion of Lion's Landing.
The Measure of a Leader-Wrathion offers this when you have phased Krasarang Wilds to a battle zone. He talks for a bit about King Varian Wrynn.
The Prince's Pursuit-This shouldn't be too hard, seeing as the trek to Exalted with Operation: Shieldwall should get you to Revered with The Black Prince.

Completing A Test of Valor apparently allows access to the rest of the quests.
The Lion Roars-this isn't too hard to do!
A Change of Command-time is of the essence, so a raid group is required so you can DPS Warlord Bloodhilt down fast so that the Horde doesn't arrive and try to disrupt the raid. Tactics can be found on his page and the Wowpedia entry.
Call of the Packmaster-the [item=93403] is rewarded, along with the Chapter II achievement.

Spreading this information around so that people will see it.

Please be aware that the prismatic socket given by this item is a ONE TIME USE. This means once you use the Eye, it is gone from your bags. Wrathion does not give an option to obtain a new one like he does for the legendary gem.

This means that if you have only the LFR or Normal version of your Sha-Touched weapon, and you know that you will receive, or have the opportunity to receive, an upgraded version of the weapon, you would be wise to save your Eye of the Black Prince, otherwise you will end up wasting it!

EDIT: As of Tuesday, January 8th, the Eye of the Black Prince is now purchasable at the Valor Point vendor in Niuzao Temple for 2500g base price. That price will change depending on guild level or if a Goblin. The eye itself is still a one-time use item, but you can safely use them on any Sha-Touched weapon without worry of not getting a 2nd one. :)