The Sentient Milieu was an association of starfaring races that existed near our region of space 25,000 years ago. It was founded by four races (of which only the Drall and Mael-Num are known), and developed over the course of several thousand years to "mutually enrich their respective cultures, to provide a safe creche for emerging sentient species and to afford themselves a degree of protection from external hostilities via military alliance," as the Melnorme put it.
It spanned five hundred light years and a hundred member worlds. However, the exact location and extent of this region that the Milieu covered is unknown due to the scarcity of information on the Milieu and the uncertain relationship between light years and standard HyperSpace distance units.1 The only other hint at the extent of the Milieu is the earlier research of Tzzz-Tzer-Tzak, which, according to Commander Hayes, indicated that the Taalo was the "only species in [the Milieu] who actually lived in our region of space".
The Milieu disintegrated as the Dnyarri telepathically enslaved member races and turned them against eachother.
The alliance is said to have included over 100 members, of whom only seven are known.
- the Drall, one of the four founding members, exterminated at the Dnyarri's command
- the Faz, joining about 22,000 years ago, slave-shielded by the Ur-Quan Kzer-Za
- the Mael-Num, one of the four founding members, ancestors of the Melnorme
- the Taalo, presumed to have been exterminated at the Dnyarri's command, possibly fleeing to *Pretty Space*
- the Ur-Quan (still one race at that time), the last major race to join, split into Ur-Quan Kzer-Za and Ur-Quan Kohr-Ah
- the Yuli, exterminated at the Dnyarri's command
- the Yuptar, exterminated by the Ur-Quan Kohr-Ah
There are certain discrepancies between sources concerning the number of races involved in the Milieu. The Melnorme refer to the "the remaining eleven races of the Milieu"2 whom the Dnyarri compelled to exterminate the Taalo, indicating that the Milieu possibly incorporated at least five additional, unnamed races, and refer to the usual list as the "seven most active Milieu members." The Ur-Quan Kzer-Za refer to the "six races of the Sentient Milieu" and the Ur-Quan Kohr-Ah plainly refer to "all six of the other races in the milieu," which agrees with the list of members races and history found in the Role Playing Resource Guide. Finally, the Slylandro name only six Milieu races, omitting the Yuptar from the list of members. There are no known references to specific additional Milieu members beyond the traditional seven.