The psions are technically an enslaved faction that gained citizenship in the cabal empire, and there's a faction that, put very briefly, wants to return to "traditional psion culture" which is also political propaganda. So long story short, like the cabal, the eliksni, and (kinda) the hive, there are factions trying to gain power that don't really like us amongst the psions. The dead messenger mission has a lot of the lore and diologue for it. Plus sundial lore.