Pylon

Pylons are Summons created by Probius. Pylons generate a Power Field and grant vision of the surrounding area. Probius only regenerates mana while inside a Power Field. Only two Pylons can be active at one time, and if a third Pylon is summoned the first will simply be destroyed.

Background
Carved from the sacred Khaydarin Crystals found only on the Protoss Homeworld, Pylons act as focal points for the Psionic Matrix emitted by the Nexus. The floating Pylons can power any Protoss buildings within a large radius around them, and establishing a network of Pylons is essential to properly expanding a new Protoss colony.