Well, I got the idea because that's kind of how Illithids operate. They seek to create the perfect slave through various surgeries and psionic augmentation. Also because gaining power through magic is cool but I have always had a heart for physical augmentations.
As far as experiments go, you would keep human form but certainly would no longer really identify as one. He would most likely try to turn you into an Illithid hybrid. This usually starts by implanting an Illithid tadpole in your ear to take over your brain. However, due to Masriths arrogance, he could accidently put a dying and weak tadpole. This is possible because Illithids feed the weak babies to the others to make them stronger. So, instead of taking over, it melds with your brain still giving you full control but granting you slight psionic abilities. While the tadpole would try to transform your body, your skin would turn slightly purple and a light blue, your eyes may turn a little white as well. While your body is transformingredients, he would probably perform surgery and give you two tentacles on your back that could grab enemies and shoot a bit of lightning. Probably want you to breathe acid too. You would also grow claws.
You would certainly become something of a monster.
Also, I think Masrith being killed by his own experiment in the end may be a cliche, but it would give him a rival. Since everyone kinda knowsad the other generals.
If you are talking about the shipping of slaves that Masrith was gonna take, you had Sven drain all their life force. He doesn't have anything to take if their all dead, so this would prompt him to try to take a member of the group.
Is it just me or did that last one go a little into godmod territory? Seemed to take a lot of actions at once unless I'm missing a page or series of posts here, or if the kidnap attempt convo above was consent.