Groomsh

Home planet of the Groomshi. Always radioactive, now also horribly poisonous to all non-native life, and the Groomshi Council decided to poison everything to defend against The Empire.

Dr. Gloop's underwater base
I don't remember the details. This is where Hans Milken Arden was taken and forcibly cured using technology derived from Stem. (That's the incident that involved a not-yet-borged Pax shooting him in the knee. For his own good).

Council meeting place (what's it called?)
Where the Groomshi Council meet. This is probably also where the Archon is.