Successfully complete the indicated task to unlock the corresponding legendary 
weapon:

  Ageless: In Orzammar before you pick a new king, click the king's throne, set 
  three of your party members on pressure plates around the area, and use the 
  fourth to click the throne again. Kill the dragon to get the Ageless legendary 
  weapon.
  Keening Blade: Successfully complete the "Unbound" quest. To start it, collect 
  the journals from the following locations:
    1. Adventurer's corpse in Ruined Temple on the "Urn Of Sacred Ashes" quest 
    in the southwest corridor. 
    2. Brecilian Ruins' Lower Ruins in the south fire trap room. 
    3. Talk to an adventurer in Orzammar's Tapster's tavern. 
    4. Go to Denerim, then go to the dirty back alley, and fight the demon. 
  Marjorlaneses Recurve: Successfully complete Leliana's character quest.
  Staff Of The Magister Lords: Purchased it in the Wonders Of Thedas in Denerim.
  Starfang Longsword: Get the random encounter with the crater, then take the 
  Starmetal to Wardens Keep to have a one or two handed sword made.
  Summersword: Defeat Loghain's general when trying to save the queen.
  The Rose's Thorn: Purchased it in a shop in Orzammar.
  Topsiders Honor: In Deep Roads, find the three pieces, then reassemble them in 
  Ortan Thaig.
  Yusaris Greatsword: Successfully complete the "Statue" quest on the third 
  floor of the Magi Tower by selecting the statues in the following order: Left, 
  Right, Middle, then the statue near the fourth floor stairs.
  Wintersbreath: It can be obtained through the Warden's Keep DLC or by 
  purchasing it at the Wonders Of Thedas.