From The Heretic Knowledge Vault
A spell, or magical gadget, or something -- we are never sure exactly what -- that presumably allows its subjects' minds to be checked out to see if they know more than they're telling about something. Sarine offers to submit to one in the Far North, as she tries to convince the Tsuirakuans that she's telling the truth, the whole truth and nothing but the truth about what she knows about the elven effort to weaponize Senilis. The Tsuirakuans take her at her word and don't take her up on the offer, though.
Based on Sarine's facial expression as she makes this offer, one can deduce that a Mind Probe is a fairly unpleasant thing to undergo. This probably isn't a surprise.