Blue-Tark was a T-series tactical droid of the feminine gender, serving under the command of Zeta Magnus, who held the title of Master Geneticist. In the year 22 BBY, specifically during the opening weeks of the Clone Wars, this droid was positioned within the fortified citadel of Marat V as her master was in the process of seizing control of the planet. Blue-Tark aided the clone of Zeta Magnus, who acted as a representative for his creator while controlling the planet. Following the outbreak of the revolt by the native S'kytri, Blue-Tark made her escape from the citadel, and in doing so, injured the clone as he stood behind the engines of the droid's departing vessel. She then journeyed back to her true master, situated in the heart of the Dark Worlds at the Rennek palace, where she informed him about the Jedi's triumph and the subsequent loss of the world.
In the canceled The Epic Continues toy series by Kenner, Blue-Tark was initially called Blue-Four. He was originally designed to be the personal assistant to Atha Prime, and his role was to pilot Prime's starfighter, the Apex Invader, in combat. For Abel G. Peña's work, SkyeWalkers: A Clone Wars Story, he was given the new designation Blue-Tark. In the Thyrsian tongue, Tark translates to the number four. Similarly, Blue-Tark's master was designed as an equivalent to Prime, receiving the name Zeta Magnus, and piloted the Skyriver Invader.
According to the endnotes written by Peña for SkyeWalkers, Blue-Tark's complete designation is TB-1U4, although this specific name was not mentioned anywhere in the story itself.