Quest Completist
Enables you to see what quests you have completed, and what ones you have left to do.
Download for
-
Wrath of the Lich King -
Cataclysm
-
Mists of Pandaria
Wrath of the Lich King 
Cataclysm 
Mists of Pandaria Addon Details
Expansion
Wrath of the Lich King Categories
Developers
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Enables you to see what quests you have completed, and what ones you still have to do. Supports server query, allowing you to query the blizzard server for all quests you have completed in the past.
In-Game Commands:
/qc
/questc
Download Quest Completist
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