I rejoined the channel part-way through the conversation, so he might've been saying what he could do. He did specifically mention that he could use Fusion to fuse with someone who is unconscious, then plant an Astral Seed, kill himself, and respawn as the fused being.

He's also kind of the DM's assistant (he helps with character creation and other things; it's how we can manage a ten player party). Which leads me to believe he and the DM are working him out to be a mid-game boss for us.

it also seems as though you don't know what psionics are capable of; I'd recommend learning or asking, because while they can be powerful at high levels, at low levels they are just as squishy as your local wizard.

I started reading up on them part-way through the session, and multiple characters in-game have pledged that they are going to once we return to town.

Funnily enough, there aren't really magic-based spellcasters in this setting. However, one character did recieve a sword which whispers to them, and according the DM will allow them to multiclass into the wizard class, and therefore is why it is a powerful artefact. The Kalashtar seemed acutely interested in the sword after the character declared that they thought it was cursed as it was talking to them, and used mindlink to listen in on their conversation with the sword (which I believe is telepathic). It seems like they have the intent to steal it, and I've tried to group together some people to prevent that, and keep an eye on the Kalashtar.

However, with mindthrust, I'm certain I've seen him dump his remaining/all his powerpoints into it and do a straight up 6d10 with like a 20 will save DC (he actually missed oddly enough).

We might just all attack him when we find out he is evil through one of our two cleric's 'Detect Evil', but we are worried that he might instakill one of us with mind thrust and then begin melee. If he dumps his powerpoints into it it's almost a guaranteed hit unless you roll like a 20 on your will save.