In this game someone needs to officially say 'Do NOT Release the Kraken' and the Kraken NEEDS PSIONICS. It is screaming for psionics. Think Illithid on Darksun sized Steriods, especially the way the art turned out. That Kraken needs to be able to do Mind Flayer like blasts, but a huge radius of effect. The DC needs to be high like DC 30 or 35 or 40 because this monster is something high level characters are fighting. The module says 8 to 16. What is the average Will save of a 16th level character? what is the higher end of a Will save? In DCC terms that is level 4 to 8th level characters. I'd say most of those characters will have a Will save of +4 to +8 because magic, magical items, etc. and a good average might be +5 to +6 if you stack all these things, not just their base Will power. If DC 25 that is a 17 rolled to save. That might be enough, but if characters can conceivably get higher bonuses again via stacking things that allow save bonuses, a higher DC is possible. It needs to be scary to high level characters and unfathomable for lower level characters to think they can ignore the will of the Kraken (get it unfathomable, the sea?) The save should be against Stun so if you fail, you could be losing actions or action points since this is 5e and you get like two half actions plus bonus. I'd say if you are stunned you can't take bonus actions or 'free' actions as you can't will them into activation. But I could see someone being allowed a single Move action. Not teleport, not running, just a move. I suppose flying creatures could maintain a slow flight. Give this some thought and of course, its 5e so align it with the 5e rules. I think the psionics should be expanded beyond this. I love old school psionics so Tower of Iron Will and other things will help against the Kraken and the Kraken should have other nasty mental powers. You could also allow the Kraken to Astral Travel so it can go to the surface and that is one reason it wants to physically escape. Maybe it has a rival Kraken who lives on the surface and they hate each other or they are best buddies on Team Kraken. That would be a nasty thing to meet on the Astral Plane. Githyanki, Mount up Project Out (get it, astral projection).