I’ll join soon a Rappan Athuk game.
We’ll start at level 1 and party will be of 6 characters.
As 1st character I decided to do play an elf Diviner Wizard, opposition schools Ench/Necro, abilities 7/18/12/20/11/7. DM Ban: Exploiter Wizard.
Could you present to me any interesting and valid build, given the deadly adventure we are going to face?
Never played this particular adventure, nor have I ever played a Wizard, but here is my advice...
At low levels, use your Forewarned/Diviner's Fortune ability to buff the party's beast mode character in the surprise round.
Prepare lots of defense spells you can spam on your party...
Prepare lots of utility magics to be the guy that gets through the random stuff...
Mend/Craft as much as possible to be useful...
Use/abuse Aid Another any time you can't justify moving to cast a spell...
If you can take a Drawback (Warded Against Nature?/Umbral Unmasking?), see if you can snag the Arcane Adept Package Equipment Trait, so you start off well-prepared.
Honestly, if you live long enough, you can take Additional Traits later on, saves, skills, BS metamagic reduction tricks, whatever...
If you can start with three traits and a drawback, you can feasibly have 1000gp worth of gear, a +1 Reflex save, and a +1 Fort save @ level 1... so a wet fart doesn't kill you.
After you get your initial Wizard crap out of the way, feat-wise, you can take Additional Traits for the +2 Initiative and whatever metamagic reduction nonsense spellcasters do.
It might be worth looking into a more well rounded trait than the combat/regional trait for +2 initiative...
You can get a +1 initiative AND +1 concentration checks with a magic trait..
Leaving you with a completely free to choose trait.
I'm an idiot...
Initiative is clutch!
Take the magic trait for +1 initiative and +1 concentration checks, first and foremost.
Take the well-prepared traveler trait.
Take a drawback for a useful skill trait.
Then, after all the normal Wizard feats, take Additional Traits to bump your your Fort save and your Reflex save, if you want/need...
I don't know much about playing a Wizard, but going first always helps, and being able to concentrate is important for your class...
A +1 to concentration checks is worth a quarter of the Combat Casting feat (and stacks with it!), from a trait that still provides a +1 bonus to initiative!
Given you're an elf, might be worth considering *not* tanking your strength; just keeping a 10 will allow you to longbow away productively. There's seriously very little rest in Rappan, you're going to be down to cantrips pretty early in the day.
A Str10 wizard will be better with a light crossbow prior to Haste, or BAB6 (which is 12th level for him). So keep that garbage at 7 where it belongs. (And EWP:Repeating Heavy Crossbow is not the worst idea in the world; buy a couple of things and toss them in your haversack.)