Before you can see Lord Vader, you need to complete the quests of Kaja, Loam, Hethrir, Thrawn, Veers and The Emperor, in that order.

Vader is located by where you went to see Colonel Veers and Captain Thrawn. In the hallway there, instead of making a left towards the balcony door, proceed straight, then make the first left, then immediately a right through a pair of large machine doors. There will be two stormtroopers there waiting and you know you have the right room. Walk directly across the room towards the curved part in the wall and once you are standing almost right on it, it will open and Vader will be standing there.

This is a small delivery mission with one bonus, Mara Jade. The agent for the Master is actually Mara Jade. Check her out in a rather neat looking leotard with red and grey web pattern. She even has the facial scar.. is she supposed to? Who cares.. its Mara.. *purr*.

Pickup mission from the Emperor's Hand. No nasties near her. Interesting though, she had a blue I above her, have to return and see what missions she gives.

Reward: 20 Imp FP and 500 Credits.

Side note: Went back to Mara Jade and got message: You're not working for him, I take it? If you're not, it would be in your best interest to buzz off.

Her location (for me) was 2597,-4275 (close to emp retreat)