At a Moebius Foundation base explored by Zeratul and Talis, the found numerous pylon containment units being used to control pylons. The pylons allowed the terrans to utilize warp-in technology, something that surprised the protoss. They destroyed the containment units and took control of the pylons back for their own use.
The pylon containment units contain enemy pylons. When the units are destroyed, the pylons inside become vulnerable and automatically come under the player's control, and they automatically receive a number of new units that warp in.