In no particular order, here is my list of "necessary" skills - have I missed anything?:
* Great dialogue skills
* High Disable Device/Search
* "Defensive" tank with evasion and spell resistance
* High level sorceror (relative to party level, e.g. few or no levels in other classes, -1 ECL max)
* High level cleric (see above)
* A monk for the Eight Chambers
* Wilderness Lore
* Lightning spells for the Guardian
Accordingly, here is what I came up with. I'm not really soliciting character creation tweaks, as the party will be joining Oswald for the second time by the time I finish my next gaming session.
1) Rogue/Bard (Human) - currently Ro2/Brd11. Level progression was Ro1-Bard5-Ro2-squat-Bard11. Rogue levels for evasion and class access to Intimidate, Bard levels for songs and spells, Bluff and Diplomacy. Now has GSF: Enchantment, 15+ ranks in all talking skills, and buff spells. Covers off dialogue requirements and numerous buff spells, freeing up spell slots of sorceror and cleric, since my wizard is lagging behind in levels. Originally planned to add one more rogue level and four fighter levels, but I might not. Bards are a "special" spellcaster, in the sense that they do not access their highest level spells until bard lvl 26. Also, this character hasn't killed anything since a Malarite at the Shaengarne Dam, so it's not like I need weapon specialization. Do you recommend continuing all the way with the bard, or taking a few fighter levels?
2) Monk/Illusionist (Deep Gnome) - currently Mk10/Ill1. Level progression was Ill1-Mk10. Hoping to end as Mk20/Ill10. Covers off my defensive tank and monk requirements. Has the illusionist level for minor spell assistance, and learning spells. This is an experimental character, to see if I can "improve" on the generic monk. For those interested, AC gets into the high 40s when buffed and using Expertise. I think I could get higher for short periods of time, but why bother? I can't remember the last time this character got hit on anything less than a critical. I could add Shield to my regular buffs to up the AC into the low 50s, I think.
3) Pal/Sorc (Aasimar) - currently Pal2/Sorc10. Level progression was Sorc6-Pal2-Sorc10. Standard bomber. No buff spells except Shield, Mirror Image, and Stoneskin.
4) Ro/Ftr/Pal/Wiz (Drow) - currently Ro3/Pal3/Wiz7. Level progression was Ro2-Pal3-Wiz7-Ro3. A mid-game rogue level means you have a high level-based cap on your skills, allowing me to put ~15 points into the disable device and search skills - I hate just walking through traps, and having to buff up to disable traps in the later game, as you often have to do with a Ro2. The character wasn't very good as a Ro/Pal, but is now a capable archer, caster, and melee fighter. This character got How to Be an Adventurer because I needed to give a boost to the wizard levels.
5) Barb/Ftr/Druid (Human) - currently Barb1/Druid12. Level progression was Druid1-Barb1-Druid12. Took 2 ranks of Wilderness Lore as a barbarian and 2 more as a druid, which was enough to get through the Fell Woods with ease. Concentration is not as high as it could be, because my low Int meant I had to put more points into Spellcraft to overcome the negative Int modifier to get elemental feats. I'm playing the character as the primary damage-dealer to enemy melee units, either with spells or weapons.
6) Cleric of Lathander (Aasimar) - currently Cl13. Your standard healer and buffer, with some offensive capabilities. I went with a low Int, average Cha build to try and get some use out of Turn Undead. The downside is that I won't get Spirit of Flame any time soon, although I do have GSF: Evocation.