HELIOS-3E was an IG-86 sentinel droid who was affiliated with Cad Bane, a bounty hunter.
Cad Bane enlisted HELIOS-3E's help on Coruscant after receiving instructions to retrieve the blueprints for the Republic Executive Building. Todo 360 successfully isolated C-3PO, Padmé Amidala's protocol droid, from R2-D2; subsequently, 3E arrived in a speeder to transport 3PO to Bane. Upon learning that R2 possessed the data for the Republic Executive Building, he and Todo were dispatched to locate him. After a fruitless search for the astromech, they returned to Bane without success. R2-D2, upon hearing about the torture of C-3PO, surrendered himself to prevent further harm to his friend. The plans were then extracted from the small droid, and 3E was tasked with erasing their memories and "dumping them back on the streets."
Later on, during the Senate hostage crisis, 3E aided Bane by guarding the hostages. He later made a successful escape from the crime scene along with the rest of the team and Ziro Desilijic Tiure.
As an IG-86 sentinel droid, HELIOS-3E functioned as a bounty hunter within Cad Bane's group. 3E was programmed with masculine characteristics and stood at a height of 1.96 meters, equivalent to 6 feet and 5 inches.
HELIOS-3E exhibited a degree of apprehension towards Cad Bane, understanding that his master would be displeased by his and Todo 360's failure to capture R2-D2.
3E was an assassin droid adept in combat, piloting, military strategy, and data slicing.
3E carried a long-barreled blaster rifle as his weapon.