HK-1

HK-1 was an patrol droid stationed on the Endar Spire during its destruction. This droid was initially damaged during the attack but was brought back online by Rarth Devan to help him eradicate some Sith troopers. The droid was left onboard the Endar Spire (for some reason) but survived its destruction due to a simple fluke.

As the ship's hull was breached, it experienced a hyperdrive malfunction. The hyperdrive fired, blasting the ship away but giving the illusion of an explosion. What was left of the ship came to rest on Mustafar. HK-1 and several other droids took it upon themselves to defend the ship.

For five thousand years they stood watch over the ship, and during that time the Galactic Civil War started. Rebel Scouts descended to the planet and found the ruin, extracting records of Trask Ulgo from its remains. HK-1 attacked the group, took the records and escaped to parts unknown, his droid possy not far behind. The Rebels had to call for another ship to make it off the planet alive.

HK-1 presumably took the files somewhere safe, to make sure no-one ever found out about Trask. He is possibly still guarding them now. Of course it is also possible that this droid was (somehow) Trask all along... stranger things have happened...