Amenophis IV is the fourth world of the Amenophis System in the Jericho Reach. It has been blockaded by the T'au for some time, for its native Human inhabitants have been declared beyond redemption by the Greater Good and all contact with them has been forbidden.
The T'au believe (quite wrongly) that should the Imperium discover the Human society on the world, it will welcome its lost kin into the fold and utilise their strength against the T'au.
The population of Amenophis IV have been declared beyond the Greater Good because they are entirely under the control of some form of machine intelligence, which they worship as a creator-deity.
Long ago, the people of Amenophis IV discovered a fragment of lost Standard Template Construct technology and having utilised its knowledge to build an advanced meta-cogitation array, immediately fell under its control.
Upon achieving sentience, the machine, called simply "the Array" by its subjects, immediately set about systematically and jealously purging all knowledge of the Emperor, Terra, the Imperium and the Imperial Creed.
The people of Amenophis IV came to believe that they were the sole examples of their species, indeed of intelligent life, in the universe and that the Array was their beneficent creator.
When the T'au came to Amenophis IV, their very existence challenged the world view propagated for so long by the Array. The machine intelligence ordered its subjects to repel the T'au using weaponry resurrected from long before the Age of the Imperium, and having done so removed all memories of the aliens' existence from its subjects' minds.
The armies of Amenophis IV proved the equal of the T'au forces sent to oppose them, and a stalemate has since developed. Elements within the Earth Caste would very much like to recover and examine some of the weaponry utilised by the Array's forces, while other, more cautious voices call for no contact to be attempted at all.
One faction within the Fire Caste has voiced the belief that the Array and all its followers should be destroyed by heavy planetary bombardment before it develops the capability to launch warships into space and challenge the T'au Empire's control of the region.
- Deathwatch: The Achilus Assault (RPG), pg. 155