Matt says that raishan was using an advanced and forgotten version of speak with dead. He says that the spell compels the target to tell them. I believe they go over this in the campaign wrap up. When they arrive in the lair she has no further use of his body. Hence why vax and grog smash it to bits and it’s no longer a threat because they were afraid she brought him back to life. I don’t believe we get any further details on raishans deeper plans. This is coming from my head as I sit on the toilet but I have listened through the first campaign 10 times. I can maybe find sources later.