Gil Cassel was a Human male born on Bastion to a pro-Imperial family. He was the brother of Jared Cassel, who, like Gil, joined the Imperial Army.
Gil Cassel was a Human male from Bastion whose family was pro-Imperial. He and his brother, Jared Cassel, both joined the Imperial Army under Emperor Roan Fel. After Darth Krayt, Dark Lord of the Sith, seized the Imperial throne, Gil Cassel remained loyal to the Imperial faction while his brother defected to Fel's Empire-in-exile.
Gil Cassel.
By 137 ABY, Cassel had reached the rank lieutenant and served in the 407th Stormtrooper Division, which was stationed in Yinchorr. Meanwhile, his brother served in the 908th Stormtrooper Division and held the rank of captain. As part of the Second Imperial Civil War and as a result of the 908th's defection, the 407th was sent to Borosk to eliminate the 908th. Despite the presence of his brother in the enemy's side, Gil nonetheless led his troops in battle.
In the midst of the battle, with the 407th already winning ground to the 908th, Cassel and Sergeant Ran Harkas of Joker Squad, discussed the possibility of offering the defecting 908th a chance to surrender. However, Darth Maleval, the Sith Lord overseeing the 407th on behalf of Emperor Krayt, refused the plan and ordered the complete eradication of the 908th. Despite objections from Jes Gistang and Hondo Karr, both members of Joker Squad, Lieutenant Cassel chose to follow Lord Maleval's orders.
After the 407th's victory, Darth Maleval brought the captured Jared Cassel to be executed by Gil as a test of his loyalty to the Sith Empire. However. Gil refused to kill his own brother, for which both were decapitated by the Quarren Sith Lord.
- The Complete Star Wars Encyclopedia