The Battle of Borosk was an engagement caused by the resurrected Darth Krayt's military push across the galaxy. Following Borosk's capture by the Sith Empire in a previous battle, the planet's control had gone back and forth between Fel and Krayt. By 138 ABY, the planet was back under the control of Fel loyalist forces.
However, when the Sith-Imperial forces returned to take the planet, the Bastion forces were overwhelmed. Master Rand Ko, the Imperial Knight commanding Fel's forces, was ordered to retreat by his Emperor. As Roan Fel finished delivering his orders the holocomm link between Fel and Ko was cut short. The last Fel saw of his loyal Imperial Knight was him being attacked by a Sith Lord.