Quel'Delar

Quel'Delar, the Sister Blade is a prismatic blade forged by the night elves and the five dragonflights along with its sibling,. Quel'Delar serves as an idol of opposition against the Scourge, and the elven factions of Dalaran would therefore like to see the blade play a pivotal role in the assault on Icecrown Citadel.

Players are able to embark on a mission to assemble the sword and either wield it themselves or trade it with their respective Dalaran faction for a weapon they can use. Doing so will reward the achievement.

History
After its creation, the sword was given to the quel'dorei and passed down from father to son until it was wielded by Thalorien Dawnseeker against the trolls and the Scourge. Thalorien eventually fell at the hands of Arthas' lieutenants and the blade was subsequently brought to Icecrown by Lana'thel, one of the followers of Kael'thas. Lana'thel originally intended Quel'Delar to be an instrument of vengeance, but after her own demise began to harbor hatred for the sword.

Now that the Ashen Verdict, alongside the Horde and the Alliance, are ready to march upon Icecrown Citadel, interest in the sword has been renewed. When Lana'thel defiles the sword at Quel'Delar's Rest, the Silver Covenant and the Sunreavers immediately vow to return the blade to its former glory, so players are asked to reforge and cleanse the sword. The whole process takes players to distant places like the Halls of Reflection, the Sunwell and Dalaran.

The blade is now rumored to be borne by a new master.

Discrepancy
Lorekeeper Lydros implied that there were many Quel'Serrars and one "Prismatic Blade of Quel'Serrar." However, the lore about Quel'Delar says that there were many Prismatic Blades, with Quel'Delar and Quel'Serrar (oddly having the name of all of them) being sisters, and does not mention the many one-dragon Quel'Serrars.

Quel'Delar in the Halls of Reflection
In the Halls of Reflection, the character must "subdue" Quel'Delar. Quel'Delar fights much like a warrior, using Bladestorm, Heroic Strike, Mortal Strike and Whirlwind. It not only can be disarmed by a warrior's Disarm ability, it has been reported that other methods might also work. (Note that where disarming works, it does not automatically result in victory.)