The world of Ea is dominated by deep seas of a vivid violet hue and studded with numerous chains of small islands. Despite now being under the control of the Velk'Han Sept, the world has no native population and has been sequestered by the members of the Ethereal Caste as a retreat and sanctuary.
Only the Ethereals and their most trusted honour guards are allowed to set foot upon Ea, and all others are forbidden from leaving their vessels, which are required to hold station in orbit high above the world.
The Ethereals' retreats take place in ancient stone structures built by a long-extinct species eons ago. Apart from these structures, no other trace of the ancient civilisation has been found.
The Ethereals are thought to seek peace and inner harmony amongst the cyclopean halls and high atop the rearing towers of Ea, meditating for solar weeks on end on the proper path the T'au Empire should take.
Given the concentration of such highly ranked individuals in one place, the T'au allocate significant resources in ensuring its existence remains a secret and its borders secure. A large fleet patrols the system and its outer limits, ever watchful for enemy incursion.
Initially, it was the agents and Assassins of the Imperium that the fleet was guarding against, but recently its concerns have focused on the possibility of infiltration by Tyranid vanguard organisms. To date, none have been discovered, but the warships of the Air Caste remain alert for the slightest sign of Tyranid incursion.
- Deathwatch: The Achilus Assault (RPG), pg. 115