The Hawke's Key

The Hawke's Key is a plot item and weapon equipped by Hawke in the Legacy (quest) in the Legacy DLC for Dragon Age II. Uniquely, the identity of the weapon will automatically vary depending on Hawke's class.

Background
"'The key is, and always will be, part of the cage that holds Corypheus. The prison's power is tied to that of the key; as the power of one waxes, the other wanes." "The key's origins are lost to time. All we know is that it is an ancient, powerful weapon. The Wardens of old uncovered a few of its secrets - just enough to draw upon its magic to create the seals that hold Corypheus." "Accounts indicate that the key attunes itself to whichever man or woman wields it in the rituals that reinforce Corypheus's chains. It is the nature of the magic, something in the blood. The key is currently attuned to one Malcolm Hawke, the last mage to hold it." "The key is an essential part of strengthening the seals, and also the only thing that can break Corypheus free.'" "-From Janeka's research notes."

Acquisition
The key is acquired by defeating the Carta dwarf Rhatigan in the Carta Hideout (Legacy). The key is then automatically equipped as a weapon which varies depending on Hawke's class.

Mage Hawke
For mage Hawke, the key is a magical staff.

Rogue Hawke
For rogue Hawke, the key is a dagger.

Warrior Hawke
For warrior Hawke, the key is (to be confirmed).

Plot Involvement
The key is also used as a plot device in the Legacy (quest). See that page for further details.