BT-1 assassin droid

"Not exactly. This is BT-1, a "Blastomech" prototype. Does enough to pass as an astro, but it's primarily a cover. It's a specialized assassin droid."
 * "All this effort for a simple astromech?"
 * ―Darth Vader and Aphra talking about BT-1.[src]|undefined

BT-1 assassin droids, also known as Blastomechs, were a type of assassin droid that were designed to look like ordinary astromech droids.[1] AppearancesEdit
 * Star Wars: Darth Vader 3: Vader, Part III (First appearance)
 * Star Wars: Darth Vader 4: Vader, Part IV
 * Star Wars: Darth Vader 5: Vader, Part V
 * Star Wars: Darth Vader 7: Shadows and Secrets, Part I
 * Star Wars: Darth Vader 8: Shadows and Secrets, Part II
 * Star Wars: Darth Vader 9: Shadows and Secrets, Part III