I am making this post on the assumption that you were a solipsist (since you talked about playing one a few posts ago), and will just talk about them.
Edit : Nope, couldn't win. In High Peak I just started getting instagibbed, for no apparent reason.
Yeah, high peak is kind of ridiculous hard even as a solipsist (I lost 4 of my lives there). I think its because you go 95% of the game being completely immune to 99% of all the enemies and being able to melee them to death without even using talents, then go to a place where you take real damage from every attack. You don't expect it and think you can sit in melee range of that rare/unique for like 5 turns and be totally fine, when since he is level 80 he kills you in two turns.
You really should just ignore the rares and get up to the final level ASAP.
Going into the final battle you need: A movement infusion and the controlled blink ability.
There are a bunch of other abilities that *really* help, but most are fairly optional.
With those two movement abilities you can close all of the portals fairly fast (tele to one, movement infusion to the other, and do it again in 10 turns).
Stay in line of sight of only one of them at a time (otherwise they will do +500 damage a turn), and use as many summons as possible as often as possible to distract them (mind-forms, yeek mindslayers, inner demons).
Inner demons is great, and will basically stop them cold till the deamons all die.
Use as many abilities that block LOS and screw up their movement as possible to ensure only one can see you (eg. distortion vortex, dreamforge wall summoning ability).
Use your telekenetic link to stop blinding from effecting you.
Most importantly, don't think that you are tough as a solipsist if you are fighting them (which I did till I died against them once after 5 turns of fighting) since they can do comically high amounts of damage, if you have less then 75% psi (and one or both aren't disabled) make sure you are healing or escaping *to* heal
I had absolutely no idea whether to stack resistances, armor, defence, status resistances or saves, and I couldn't get all of them, especially since the best randarts I found were powered by arcane forces. So I tried to get all the resists I could, but I kept getting stunned and frozen, then I switched some gear for stun resistance, but just started getting blinded instead, and in the end I started taking way too much damage to handle.
Honestly, I didn't find AM worth it for my solipsist, there are so many great arcane items and runes that it really hurt not being able to use them, I kept forgetting to put my AM shield on when I needed it, the first ability in the tree isn't much better then divination, and you already have a comic amount of damage shaving, so a bit more is kind of MEH.
Not being able to use the runes and items really hurts a lot.
Note that the below advice applies *only* to solipsists, every class has different needs.
For defensive choices:
Resists: Get as much resist-all as possible (rank 5 thick skin+rank 5 of the ability that means that your summons gives you bonuses), and just try to get all the others as high as possible in general.
Armor: Pretty useful most of the time, you probably want to get the best plate armor you can wear, and don't bother with it after that (besides the dreamforge ability)
Defense: Don't really bother, more is better, but don't chose items for how much they give you, since you won't really be threatened by melee attacks and the other things you get or better.
Status resists:
Stun: Very nice to have a resist of, but not super critical, you can just run away (or use abilities to block their sight, or knock them back, or teleport away, or use a movement infusion or put them to sleep, or use summons).
Freeze: Rather annoying, but its not very dangerous *usually* since it blocks 60% of the damage you receive, and the rest probably won't do much damage past your sheilds, if you really need to get away you can use a infusion to break it then escape.
Blind: Use telekinesis on the boss/rare, and now being blind doesn't matter
Anything mental: Use your mental blocking ability
Anything magical: Use a infusion/remove all ability (The chase is on or whatever its called), you can't really do anything else about these if they get past your saves.
I really don't think I'll be playing Tome 4 anymore, or at least for a while. It drags on and on and on, runs worse than Diablo 3 later on, and I'm starting to find certain parts of it retarded. Like the 20 different kinds of resists, damage, status effects and item stats; the ridiculous talents random rares can spawn with; and mostly, getting attacked outside of LOS. Sorry Tome, that's bullshit and there's no way you're convincing me otherwise.
Yeah, the pacing starting in dreadfell gets really bad, going from fresh and quick to slow and tedious (for me at least).
Yeah, the dozens of different resists are huge pains in the ass.
As is getting attacked from out of LOS (although by the end of the game that stops happening since you get +6 light radius lamps).
Getting instakilled (from max->0 without a single action) is complete bullshit, and they should try to reduce how often it can happen (but as a solipsist you don't ever really need to worry about it).