During the Reclamation of Aiur, several void pylons were found on the surface of the Aiur. When Dark Prelate Zeratul attempted to find Hierarch Artanis, he discovered three void pylons, which he used to summon stalker reinforcements.
Void pylons are found in the Legacy of the Void campaign mission The Growing Shadow, and function the same as normal pylons, only with increased health and shields. When uncovered, they provide the player with stalker reinforcements. Three void pylons can be found on the map.