The Twin Jian was a Water/Fire epic boss from June 23rd to June 29th, 2013. It dropped Fused Feathers which is used to craft a Jian's Battlegear. Jian's Nemesis Mail was available in the Dark Prince's Chest during the event.
The Twin Jian had twice the normal attack and defense values, making it an extremely difficult boss to kill. It gave twice the normal rewards, however.