The Tau System
The target of Orokin colonisation, the homeland the Sentients built, and the Tenno's suppressed Old War past.
SENTIENT HOMELANDFULL SPOILERS
A Sentient homeland
Tau is no mere military base; it is the centre of Sentient ideas of family, of the future and of loss. The Orokin claim of ownership collides with their right to exist.
The Tenno past
The Old Peace reveals that the Operator fought on the Tau fronts. The Perita Rebellion makes those suppressed memories playable through the Dark Refractory.
The limit of access today
The Tau memories are reachable; the system as a whole is not open as an ordinary Star Chart region. The main story ahead follows Albrecht's trail in that direction.