Whatever the cultists are doing must be stopped. The rumors I've heard can only be true, then. The infamous Doctor Kohler must be among the cultists, practicing his arts. Look for a rise or an altar overlooking the cultist camp, slay the doctor, and look for proof of his plans. Slow down his work in any other way you can.
Did you find out what they're doing with the Black Knight's remains?
The doctor will not have time to complete his work, but his plan is already in motion. From what you've reported, the Lich King's servants have reanimated and empowered the Black Knight and there's no telling what the knight's master has in mind. You have done well in uncovering this plot. I will tell High Crusader Adelard of your findings and together, we will alert the tournament's participants.
Fly due west of the tent and up the hill to the new camp. There's a raised platform near the west end of the watch. In the center of the platform is a freshly undead Black Knight sitting in a green bubble being channeled by two Sacrificed Aspirants. The corpses of the aspirants are being tended by Dark Zealots. Also around is Kul the Reckless in the Black Cage and Doctor Kohler. Kill him and loot , then fly back to the Tournament Grounds.
There is currently no followup to this quest as of build 10026, 10048 on the PTR.
-  -or- 
- After reaching the rank of Champion:
- Starting in Patch 3.2.0:
Patches and hotfixes
Patch 3.2.0 (04-Aug-2009): Added