Nader Yuellen was an Imperial Navy officer with the rank of commander. In 3745 ELC he was the First Officer of Helia Thande in the heavy carrier ICS Disputer (→LOTD).
The commander was credited by Thande as being good with engineering and physics. She also found his smile 'warm and sincere' (→TRD).
He was the first person to inform Elm Caden of the damage wrought on Fort Kosling by Amarist Naeb, and almost prevented Caden from transferring his prisoners from Woe Tantalum to the Disputer. He also indirectly allowed Maber Castigon to track down Caden by supplying Kabis Boretto, captain of the civilian hauler Leo Fortune, with the transponder ident of Caden's borrowed shuttle (→LOTD).
Yuellen was present during many of Thande's conversations with Shard Caden, at least in part, and of course was an integral part of the captain's command staff. He had immediate access to all control protocols on the Disputer, as well as privileged access to the restricted Act-Con communications channel.
His actions during the Battle of Meccrace Prime are therefore deeply worrying.
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During that battle, while Imperial starships of the Eighth Fleet fired on each other, Captain Thande was almost murdered by Yuellen. He was overpowered and immobilised by other bridge officers, but began to taunt Thande as the battle progressed.
Thande noted that the taunts were completely out of character for Yuellen, and later discovered that he was acting as a mouthpiece for the entity known as Voice.
Yuellen was killed when Thande — perceiving him to be an ongoing threat to her crew — shot him through the heart (→LOTD).