A brief conflict occurred in 18 BBY on the Imperial Lambda-class T-4a shuttle known as ST 321. While traveling from Yinchorr to Coruscant via the shuttle, Emperor Palpatine and Darth Vader found themselves under attack. The assailants were the treacherous Emperor's Hand Sheyvan along with six clone warriors derived from the Dark Jedi Sa Cuis. After the attackers seized control of the vessel, Vader, together with Lieutenant Erv Lekauf and his clone troopers, was compelled to fight the Dark Jedi.
Sheyvan engages Darth Vader.
Using flamethrowers, the Lekauf clones incinerated four of the Cuis clones; Vader then used the Force to choke the remaining two. Sheyvan engaged Vader in a short duel, attempting to sway him against Palpatine, but was ultimately killed. Following this incident, the Sa Cuis clone template was discontinued, although the Emperor did not dismiss the possibility of cloning a Force-sensitive army at some point in the future.
During the engagement, Lekauf sustained burns. Vader's subsequent care for Lekauf significantly contributed to the latter's deep respect for the Dark Lord. This respect was later passed on to his grandson, Jori Lekauf. Jori would later allude to the wounds his grandfather received during the aforementioned battle.