After being discovered by the T'au Air Caste, the Water Caste extended the Thraxians honourable greetings and an invitation to join the T'au Empire, offering them mutual protection, new trade opportunities and the exchange of technology.
Under the Ethereals' guidance, they were absorbed into the T'au commonwealth.
On page 10 of Codex: Tau Empire (6th Edition), the Thraxians are stated to have been annexed during the First Sphere Expansion, but on page 28 this event is dated to 896.M40, during the Second Sphere Expansion.
The idea of the annexation occurring during the First Sphere Expansion is maintained in Codex: Tau Empire (7th Edition), but again Codex: T'au Empire (8th Edition) repeats the same conflicted information as the6th Edition codex.
- Warhammer 40,000: Rulebook (6th Edition) (Digital Edition), The Alien Menace
- Codex: Tau Empire (6th Edition), pg. 10, 28
- Codex: Tau Empire (7th Edition), pg. 8
- Codex: Tau Empire (8th Edition), pp. 12, 36