The Imperial Terror Trooper program was a possible sucessor to the Clone Assassin from the Clone Wars era. Terror Troopers seemed to move and dodge in the same manner so it is probable they were taught Teräs Käsi , a martial art meant to combat jedi. Terror Troopers seemed to be stored on Kmaino when not in use alluding to them being cloned from a single source unlike generic Stormtroopers who by this point where cloned from a myriad of sources or were enlisted from birth born recruits. Terror Troopers appear to teleport when infact they are very agile and equipped with the Shadow Stormtrooper cloaking device.
The first reported usage of the Terror Troopes was during the raid of the Rebel Alliance medical ship Salvation. Commanded by Boba Fett the Terror Troopers raided and kill the entire bridge crew along with a good portion of the patients and other crew members. The msiion was to capture Juno Elcipse to use as bait for the clone of the Secret Apprentice. The Terror Troopers were used by Boba Fett to cover his extraction. The troopers perfomred well though were eventually wiped out by the cloned jedi. Terror Troopers were next sighted during the battle for Kamino where they partnered with the Saber Guards and Sith Acolytes to reple the Rebel attack. atleast the majority of these groups were wiped out during the battle in particularly by Rahm Kota and the cloned Secret Apprentice.
Terror Trooper armor was reminisisant of Phase II Clone trooper armor and General Grievous' own armor. The clawed hands are similar to Starkiller's vision of his darkside future self the Sith Stalker. Terror Troopers use of the Shadow cloaking device coupled with their extreme agility make them seem to either flash step or teleport. They clawed hands allow for deadly hand to hand combat and Terror Troopers carried stun guns to incapacitate targets foe assassination