Dual Swords is an epic One-Handed Dagger that is rewarded upon completing the Ranger scanner quest chain. Contrary to the name, Dual Swords is one dagger.
Obtained from Edit
Dual Swords are originally, and still primarily, obtained through the Scanner quest chain. Alternatively, Dual Swords may appear in Black Market or obtained through Lottery. However, since this is a single dagger, it will take winning two of them to be able to upgrade them into Enlightened later on.
-  All in the Family I - Travel to Coldring and speak to Chen Wei.
-  (Dungeon) All in the Family II - Find the Zhi Shui Shrine in Eternal Frostlund, and complete the trial.
-  (Dungeon) All in the Family III - Search Coldring, kill the Mist Trader swordsman, and return to Chen Wei.
-  (Dungeon) All in the Family IV - Go to Flame: The Madness in Arcadian Forest (Legend mode), and get a Scanner from Lendoerl. Use the Scanner around there to summon the mysterious warrior Qiu Yuelan. Defeat her and collect Phoenix Feathers from her. Then talk to Vincent.
You will receive:
Convenant: Dual Swords are exchanged at Chu Feng in the Mist Trader Base Camp for Dual Swords. It's a long process, often taking a while to get a Scanner, and then getting geared enough to kill Qiu Yuelan (Scanner boss) to finish the chain.
Objective of Edit
Dual Swords are the objective of the Enlightened quest chain, in which these swords are gravebound (turned into useless poor quality items) and after completing the chain they are exchanged for Enlightened Dual Swords.
Warning: Do not talk to Lu Yunfei at the entrance to the Mist Trader Base Camp immediately after getting your Scanner weapon. The quest he gives  Living Weapons is a quest chain that WILL REMOVE YOUR SCANNER WEAPON(S). Since many players don't read quest text, many have lost their weapons. The process of getting Enlightened weapons is recommended for T3.5 - T4 epic players.