Phobos

"The signal from Phobos is incredibly powerful. It might be a distress call. But then, we've never heard the Cabal send out a distress call before. Approach the base with caution, Guardian."

- Zavala

Phobos is one of two asteroid moons orbiting Mars. The Cabal used Phobos as a beachhead for their invasion and occupation of Mars when they arrived in the Solar System. Later, they somehow altered the asteroid moon's orbit for unknown reasons, bringing it significantly closer to the planet. A common belief among Warlocks is that Phobos was moved to its current orbit and is being held in place by the Psion Flayers, who are only an order away from unleashing it as a weapon.

Overview
The City Vanguard believed Phobos to potentially be the command center and staging ground of the Cabal Skyburners, who were commanded by Primus Ta'aun and his lieutenants. Presumably the Skyburners were marshaling a "second fleet" with the intent of launching a full assault on the inner system.

With the arrival of Oryx in the Solar System, the Taken have swarmed Phobos, overwhelming the Cabal and forcing them to evacuate a major base.

Locations

 * Fleetbase Korus
 * Aerodrome
 * Cliffside
 * Skyburners' Keep

List of appearances

 * Destiny
 * The Taken King