Unfortunately, we are not able to approve your plot information request. However, Valdis may still question the captured cultists, but she'll only get as much as any other interrogator might. It seems that their basic and most core belief is that as long as the turtle is alive, Malicant will linger and can potentially be restored back to power. They have no reason for this belief - certainly nothing resembling tangible proof - and their devotion is perhaps the most notable thing about them.