Darth Vandrak is 1000 years old and is the most dreadful Sith Lord ever, for his powers allow him to manipulate dreams and turn them into living nightmares in order to seed fear among the populace of the world. His powers are strengthened by his Helm of Nightmares - a dreadful Sith artifact. Like all Sith Lords, he has mastered his hatred, anger and all forms of lightsaber combat. He is a terrifying Sith Lord that spreads fear and terror everywhere he goes and will stop at nothing until all Jedi are dead. His hatred for the Jedi stems from his past 1000 years ago, when he was trying to find out what are Chaos's true intentions. When he found out, his anger was so great, he dispersed that pent up negative energy towards his enemies and sent them thrashing down to their doom.
From that point on, he swore revenge against the Jedi, Chaos and the ones who wronged him of his justice and revenge. 1000 years later, his quest is almost at an end.