Well, I pass through there and I must say I did not really enjoyed my encounter. In the end I had to cheese back by scouting ahead with Valen and web + stinking cloud + greater malison + cloudkill.
In a straight up fight my party gets slaughtered by their stun bolts. They had over 100 each of these. My party is very low level.
That Priestess and her unlimited Improved Mantle. My question is why ? Are there any strategy on how to beat this WITHOUT cheese ? I don't like using traps or laying skull traps. How do I survive this without lost ?
What the fish do is actually totally legit - I think they are all Archers using Called Shot so they hit just about anything and they hit hard. The priestess is annoying - there are not that many weapons that bypass Improved Mantle at that point, but you can use stuff like Insect Plague (which SHOULD, but doesn't prevent her from casting the Mantle again). Also, keep in mind that good summons (Mordies, Elementals, etc. but NOT Planetars) strike as +4 and thus have no trouble killing her.
Personally, I treat the rest of the city as an exercise to demonstrate the power of non-violence. Sure, you could go through killing everything that stands in your way - but why? What do you gain by doing so? 3000 XP per fish is pretty much meaningless; if you care so much, kill some of the elementals that come out of the Underdark portals and are worth at least twice as much. You get a huge number of nice paralytic bolts, but by the time you are done with the Cloak encounter, you probably have more than you will use. You also get some nice crossbows and spears - but face it, you are just going to sell the extras (and you will have extras by the time you are done with the priestess). So, use the spell Invisibility 10 foot Radius and just run through the place both ways.
And now the Mindflayers, why the swallow brain ? I noticed my char was killed instantly by this. Them being invisible I can cope with, also some of their new spells. But a one hit kill capability with limitless invisibility is a bit much.
Ok, the Improved Mind Flayers thing is not so much 'cheese' as 'playing by completely different rules'. It is the only component of Solafein that I don't use. I believe what was done there was essentially take all the methods commonly used against mind flayers and give them protection from these. Not only that, but for some reason they were given 50% resistance to all physical damage and they mostly had 90% MR. I'm fine with the MR, but the Circle of Zerthimon specifically mentions them being weak against steel. Furthermore, I'd honestly like to know how Psionics would hurt something without a brain (e.g. Mordy). That detonate thing is ridiculous - 40 damage to everyone, apparently regardless of where they are. I also don't like creatures that instakill - mind flayers are already the only non-boss enemies from whom I ever retreat. They are still beatable of course, but the operative word here would be 'tedious' - and hence not fun, so I don't use them.