From Destinypedia, the Destiny wiki
- "You are the night, a piece of the Deep, your mind is lost now, The Blighted Mind is gone and you are alone in the mists. Find your way, build your world in shadow. Your throne is small, the size of the Blight that took you. Take more, create an army. The Vex were too predictable, the Taken too lonely. The time has come. Cerberus, the Phantom Mind walks among you."
- — -Recovered from Blighted Hydra Core
The Phantom Mind is a Taken Hydra observing all it finds, it has simulated millions and keeps its now infinite sized throne world in The Shadow Garden, deep within Ganymede.