He used mental projection to control weak-minded, who survived the Second Battle of Coruscant, drawing on their energies while using them to scout out the Yuuzhan Vong.
--Star Wars Encyclopedia

Nyax is attempting to uncover a Force nexus buried in the Coruscant rubble—the site of the old Jedi Temple. This effort is the source of the disturbance Luke senses in the Force.
--Essential Reader's Companion