Dragonwrath, Tarecgosa's Rest

Dragonwrath, Tarecgosa's Rest is a staff.

It is rewarded by an epic questline that challenges those daring enough to complete it. The great staff duplicates destructive magics, and also bestows upon its wielder the ability to transform into a member of the Blue Dragonflight. Those who complete the staff won’t be the only ones to receive a reward, though. As this task requires the dedication of an entire guild, upon completion of the staff all guild members will receive a unique non-combat pet to call their own.

Dragonwrath is an offensive caster staff, with bonuses that are not particularly attractive to healers. It is said that 10- and 25-man raiders should be completing the staff at the same pace, with 25-man teams having a potentially quicker time with the "professions" part of the quest.

Blizzcon
During the 2010 Blizzcon Quest & Lore panel one guy asked for another legendary caster item. After a small discussion the guy said a staff would make him happy to which the Development Team responded that it will be done. Six months later, Dragonwrath, Tarecgosa's Rest was announced.