BT-1

"All this effort for a simple astromech?" "Not exactly. This is BT-1, a "Blastromech" prototype. Does enough to pass as an astro, but it's primarily a cover. It's a specialized assassin droid."

- Darth Vader and Chelli Lona Aphra talking about BT-1

BT-1, also referred to as "Bee Tee," was a homicidal BT-1 assassin droid created by the Galactic Empire's Tarkin Initiative. After being found and reactivated by Doctor Aphra, BT-1 and his fellow droid 0-0-0 served under Lord Vader, and when Aphra faked her own death, he and 0-0-0 continued to roam the galaxy with her.

Before activation
"Wiped out its Tarkin Initiative base before setting the place to self-destruct and jettisoning itself into space. I found it, fitted it with some stronger behavioral inhibitors but can't get it to wake up."

- Doctor Aphra

BT-1 was designed to look like an astromech droid in order to fool others, and was armed with a variety of weapons. He killed the staff of the Tarkin Initiative base in which he was created and then continued to set the base to self-destruct before jettisoning himself into space. He was found by the rogue archaeologist Doctor Aphra, who could not reactivate the assassin droid as she could not speak the R&D language the droid was programmed to understand. After Aphra reactivated the protocol droid 0-0-0, a droid capable of understanding the language, she had the protocol droid reactivate BT-1. Instead of giving the two droids to the Droid Gotra, as she had originally been hired to do, the archaeologist put them in the service of Sith Lord Darth Vader, who had tracked Aphra down to demand her services in creating a personal army for himself.

Cylo-V's replacements
BT-1 accompanied Aphra and Vader, together with 0-0-0, for their mission on Geonosis, where Aphra had heard of a Geonosian queen who was in control of a droid factory. The four invaded the queen's factory, stole the machine that constructed droids and quickly escaped. Not much later, a bounty hunter that Darth Vader had earlier hired, Black Krrsantan arrived, with Cylo-IV, a person who Vader was suspicious of. Vader ordered 0-0-0 to interrogate Cylo-IV and when 0-0-0 believed that he had extracted all information he could, he killed him. 0-0-0 told Vader that Cylo-IV was training the Emperor's possible future replacements for Vader and the Dark Lord set course for Cylo-IV's research base.

To start off his attack, Vader sent BT-1 and 0-0-0 into the base as distractions. He then proceeded to attack Cylo-IV's men from behind, with his small army of droids. As he continued into the base, Vader found two twin humans, one male and one female. The twins attacked him, using lightsabers, however it was clear to Vader that they weren't Force-sensitive. After a quick fight, the two humans were told to stop by Cylo-IV, who revealed that he was an immortal system that switched to a new body as soon as the previous was destroyed and that his current body was called Cylo-V.

Cylo-V introduced his replacements for Vader and as Vader was about to strike Cylo down, the Emperor revealed himself to be in their presence and asked to see what Cylo's replacements were capable of. Cylo started by showing off the twins from before, named Aiolin and Morit Astarte. He continued to show the rest of his warriors, until he decided to show their abilities by having them all fight each other to the death. Vader started by fighting against an enhanced Trandoshan, but in the middle of their fight, Morit killed the Trandoshan. Sidious stopped the fighting, wanting to use them against his own enemies instead of each other. Vader left Cylo's research station and waited for Boba Fett, the bounty hunter he had hired to find the person responsible for destroying the Death Star. Fett told Vader that he had found the person and that the two briefly fought, with the latter winning. Fett had figured out that the person was named Luke Skywalker.

Vader's son
Sometime later, Vader instructed Aphra to join up with a group of bounty hunters and plunder an Imperial ship for credits. After sharing the credits between each other, the bounty hunters parted ways. Vader then sent Aphra to retrieve information on Commodex Tahn, the person who buried Padmé Amidala, as Vader wanted to confirm that Padmé gave birth to Vader's son before dying. Aphra, 0-0-0 and BT-1 went to The Ante an information broker, on the Spire, who after being paid a large amount of credits, gave the three information about Tahn, including the fact that he lived on Naboo. Thereafter, they attacked Tahn's home with some of Vader's droids and then subsequently tortured and interrogated Tahn, until he confirmed that Padmé had indeed given birth to a boy, after which 0-0-0 killed him.

Aphra, 0-0-0 and BT-1 soon returned to the Ante, seeking information on Luke Skywalker's location, while BT-1 and 0-0-0 went to play holochess. The Ante quickly figured out that Aphra was one of the plunderers of the Imperial ship carrying credits, after seeing the amount of credits she was ready to give, but still gave the location of Luke. The Spire was soon attacked by Imperials who believed that one of the plunderers were there. After quickly interrogating the Ante, the Imperials learned that Aphra was one of the plunderers from before. Aphra, BT-1 and 0-0-0 escaped the Spire, before finding themselves locked in by an Imperial blockade.

Darth Vader, who was on one of the blockade ship and could not reveal that he was working with Aphra, was able to convince Inspector Thanoth that they were wasting their time chasing a thief, when they could instead attack the recently discovered base of a Rebel Alliance squadron. With the blockade gone, Aphra met up with Vader again and told him that Luke was located on Vrogas Vas.

Before finding Luke, Vader took BT-1 and 0-0-0 with him to ore-rich planet of Shu-Torun, where both the ore-dukes and the ruling family were slowly rebelling against the Imperial control. While Vader was taken to a celebration party with Princess Trios, the two droids went to assassinate the king and his servants. When Vader and Trios found the dead bodies, Vader informed Trios that from now on, she would become the Queen of Shu-Torun and warned her that if the planet kept resisting the Empire, consequences would follow. Vader then sent BT-1 and 0-0-0 back to Aphra, while he set course for Vrogas Vas.

Vader kept contact with Aphra as he arrived above the planet, but not soon after arriving, he was attacked by Rebel Alliance ships. Aphra listened as Vader's ship crashed and decided to go and save Vader, with 0-0-0 and BT-1. After landing on the planet, they found Luke Skywalker and his astromech droid R2-D2. In order to trick Luke, Aphra painted 0-0-0 yellow and tricked Luke into believing that he was C-3PO, one of Luke's allies. 0-0-0 was able to get near Luke and shock him with electricity, making him fall unconscious. When he saw that he stood no chance against BT-1, R2 ran away, with BT-1 not far behind, following him.

Aphra and 0-0-0 were eventually found by Han Solo and Chewbacca who demanded they let Luke go. A fight between the four broke out, while Luke was still unconscious. R2 soon found Luke again, who was now conscious and the two outran BT-1. BT-1 then regrouped with 0-0-0, who had lost both his arms, one pulled off by Chewbacca, one by Luke and found that Aphra had fallen unconscious in the fight against Han.

The two droids got ready to eradicate Luke, Chewbacca, Han and R2, but as BT-1 got his weapons ready, R2 sprayed oil on him, blinding BT and resulting in him shooting everywhere, giving time for the others to escape and trapping the two droids under rubble. As soon as Aphra woke up, she helped the droids out of the rubble and ordered the droids to find and secretly follow Luke. The two soon found C-3PO, whose arms 0-0-0 took, reattached on himself and left him.

Arrival of General Karbin
When 0-0-0 and BT found Luke, they saw that he was fighting Imperial troops, however they knew that Vader didn't take any troops with him. They were then contacted by Aphra who told them that General Karbin, one of Cylo-V's replacements for Vader, had arrived on the planet to capture Luke for himself. Aphra told the droids to protect Luke from the Imperial troops in any way possible. Their protection wasn't enough, as Luke was captured by Karbin anyway.

Luke was taken aboard Karbin's ship, as Vader watched it fly away. Not wanting to accept Karbin's victory, Vader used the Force to crash the ship. Luke was found again by Han, Chewbacca, R2 and 3PO, before the group was approached by Aphra, who informed the group that they were standing on a minefield and threatened to kill them all if they didn't allow themselves to be captured. As they began dropping their weapons, Leia knocked Aphra unconscious from behind. The rebels took Aphra with them on their ship and left the planet.

Further trouble on Shu-Torun
After delivering Karbin's dead body to his master, Vader was ordered to accompany Cylo-V and his warriors for their return to Shu-Torun, after the resistance on the planet became too unbearable. After arriving on the planet, Vader met with bounty hunters Black Krrsantan, Zuckuss, IG-90, Dengar, Chanath Cha, Beebox and C-21 Highsinger and told them to find and return Dr. Aphra to him.

Not much time went by before Beebox returned to Vader with a disintegrated body, claiming that he had killed her, however Vader quickly saw through Beebox's lie and killed him for it. While Vader was away, 0-0-0 and BT-1 gave some of Vader's droids the ability to leech blood, despite Vader's orders not to. The droids used this ability in their battle against Baron Rubix's soldiers, easily making their foes surrender out of fear. Vader soon learned of the two droids' actions, but had no time to care, as he had to use this chance to attack Rubix's citadel. After the execution of Rubix, Vader and his droids left it up to Queen Trios to defeat the now-weakened rebellion on the planet. Arriving back on a Star Destroyer, Vader explained to his two droids that before the attack on Rubix's citadel, Vader had been attacked by Cylo-V's two twin warriors, Aiolin and Morit, and that Morit had killed Aiolin in the fight. He also told the two that Cylo-V and the rest of his warriors had revealed themselves to be traitors, as they had aided the ore-dukes.

Vader reported to his master, who ordered him back to Coruscant, as Sidious wanted to explain everything going on with Cylo-V, but before leaving, Vader was contacted by Thanoth, a former inspector and traitor of the Empire, who informed Vader that he had found Aphra.

Characteristics
"Bleeep! Bleeep! Bleep!" "No, BT-1! No! You can't possibly do that. They are our masters! Also, who would clean up the mess?"

- 0-0-0 persuades BT-1 not to attack Darth Vader and Doctor Aphra

BT-1 was originally programmed by the Tarkin Initiative to be violent and cruel. After being reprogrammed and having his behavior changed by Aphra, he was no longer rogue and was able to be commanded. He mostly follows 0-0-0 and possibly considers him a friend.

Behind the scenes
The assassin BT-1 first appeared in Darth Vader 3: Vader, Part III, the third issue of the Marvel comic book series Star Wars: Darth Vader, written by Kieron Gillen with art by Salvador Larroca.

In the New York Comic Con 2018, it was revealed that an action figure of BT-1 is slated to see release on Spring 2019 as part of Hasbro's 2019 Star Wars action figures wave.