Who is Master Joruus C'baoth from The Last Command and what is their importance?

Master Joruus C'baoth is a clone of the long-dead Jedi Knight, C'baoth is the novel's villain, said often to be far more evil than the late Emperor and Darth Vader. C'baoth first appears accompanying Grand Admiral Thrawn during his attack on Ukio, using the Force to control precision firing by cloaked cruisers to simulate a laser penetration of Ukio's planetary defense shield, convincing the authorities to surrender. C'baoth reads and controls minds, having grown rapidly in the Force since his last attempt a month earlier.