Ru'sad is a Scourge necromancer in charge of the undead forces found in Zul'Aman. He is under command of leaders in Stratholme. He is interested in killing the high elves found in the troll forests to prevent them from rejoining any allies in Hillsbrad or Khaz Modan, in order to prevent them from reviving the Sunwell. He had sent gargoyles, ghouls, and zombies into the jungles to look for them. Brann killed one of these gargoyles during his journey in Zul'aman and found a letter written by Ru'sad on its corpse, giving hints that the lost and scattered high elves, still had importance.
To my illustrious masters,
I regret to inform you that several Quel’dorei bands still wander loose in Zul’Aman. The elves know forests better than I, and the ghouls and zombies make a fearsome amount of noise trudging through the overgrowth. The gargoyles are somewhat more helpful; they allowed me to discover one refugee group and kill them as they slept. However, I respectfully request additional support. Incorporeal troops — shades or ghosts, perhaps — would be particularly useful.
Despite the current problems, I am confident that it is only a matter of time before we finally destroy the elves. They will not join with their allies in Hillsbrad or Khaz Modan. They will not rally together. They will not revive the Sunwell.