Whew. Almost done now. You're back on the first level of the tomb, albeit on the previously unreachable eastern half. Unfortunately there was no quick ingress, but perhaps there's an egress?
Enough idle speculation. The encounter ahead can be resolved through diplomacy or combat, and if you lack a silver tongue - or the patience to wag it - now is a good time to spellbuff.
When you're ready, make your way forward into the chamber beyond, where you'll be confronted by an unearthly barbarian guardian named Zorek. Ask him what questions you will, then, if you wish to avoid a fight, pick the dialogue option "Let me tell you of my deeds - they'll make my worth clear." followed by "I'm ready. Listen well."
You should now see a string of [Diplomacy] checks and perhaps the odd [Bluff] and [Intimidate], the latter being an incredibly difficult [Intimidate 50] check. All the other checks - boasts of your deeds - serve to impress Zorek, hence making your claim, the [Intimidate] check, easier to achieve. Of course, your actual boasts depend on your previous actions, and if you say something unpleasing, Zorek may disregard your boast, or turn hostile.
If you spared either Hargulka or Tartuk, you'll have the dialogue option "I plundered Trobold, the underground monster city!", which will provoke Zorek. Likewise, if you spared Vordakai you'll have the option "I defeated Vordakai, ancient necromancer and ruler of the cyclopes!", which Zorek isn't fond of, either. It doesn't matter if you pass or fail this check, merely attempting them results in a fight.
On the other hand, if you killed both Tartuk and Hargulka you'll get the option "I killed Hargulka and Tartuk - a troll king and a kobold king respectively - and destroyed their city!", and likewise with Vordakai you'll be able to say "I killed Vordakai, ancient necromancer and ruler of the cyclopes!". These checks can be passed, and if they are, will impress Zorek and drop the DC of his [Intimidate] check.
Other feats you can boast about include defeating the Stag Lord, exterminating the Longtail tribe during the quest Lost Child, murdering the villagers of Lake Silverstep, and defeating Dugath and the rest of his barbarians. If you're a follower of Gorum (or you can lie convincingly enough about being one) that'll also appease Zorek. Successfully lying about serving Gorum is also worth a hefty bit of experience - over 11,000, in fact.
Depending on how many of these checks you can pass, you could lower the required [Intimidate] check to reasonable levels. Pass the [Intimidate] check and you'll prove your worth to Zorek by your deeds alone, earning you passage without a fight. Honestly, the experience for talking your way out of a fight is far, far greater than by winning the fight itself, so it's probably worth trying if your Diplomacy skill is high enough.
If a fight breaks out, don't sweat. Zorek's not that powerful of a warrior. He gets plenty of attacks per round and his pretty hard, but his Attack Bonus is barely higher than the Greater Skeletal Champions you fought in the previous area. His Armor Class is also high, but not on par with the Devourers or Bloody Bone Beasts you may have fought. His Hit Points aren't even all that high compared to creatures you've been fighting, nor does he have any Damage Reduction. Simply put, there's no reason why a spellbuffed party shouldn't be able to cut him down with relative ease.
While the experience favors diplomacy, if you kill him you can loot his body for a Falchion +3, a suit of Full Plate +1, a Headband of Inspired Wisdom +2, an Amulet of Natural Armor +2, a Ring of Protection +2, a Cloak of Resistance +3 and the odd potion and scroll.
Claim victory, whether through diplomacy or combat, then search the eastern corner of the room to find a hidden [Perception 35] check. You can find a body to loot in the northern corner of the chamber, while a grate to the west [Perception 9] can be searched for a Leather Scrap Covered in Ancient Runes.
If you were somehow depleted by Zorek, best rest up, because the next battle is even harder. When you're ready, spellbuff, save your game, then head into the room to the next chamber to the southwest, where you'll find Armag having a bit of a... disagreement with a Deface Sister. Unfortunately, Armag's wrath isn't sated with her, and he'll shortly turn his attention onto you, summoning a host of Greater Skeletal Champions to aid him in battle.
This fight can be harrowing for one reason - Armag himself. He's got an outright silly Attack Bonus that makes worrying about your Armor Class moot. If he's not deterred by concealment, he's going to hit, and the only question is how hard. Stoneskin will help mitigate damage somewhat, but even with that buff he still hits harder than most any foe you've fought before. On a critical hit he could quite nearly one-shot any of your warriors.
If you were hoping that he'd be something of a glass cannon, your hope is in vain. His Armor Class is higher than a Devourer's - very near forty, and he's got enough Hit Points to weather more than one lucky critical hit. All is not lost, however, as he does has a weak-point: spells. He's outright immune to Magic Missile, for some reason, but his Reflex Save is only only moderate and his Touch Armor Class is laughable, meaning a variety of spells can be employed against him with decent expectations of success.
Chains of Light has a good chance of keeping him held - assuming a caster with an Attribute Modifier of +5, this spell should have around a 50% chance of working, which may just keep him occupied for a round or two. The best way of damaging Armag is through direct damaging spells, however. Flamestrike, Hellfire Ray, Chain Lightning, Controlled Fireball... any party-friendly (or easily-aimed) spell that requires a Touch Attack or checks the target's Reflex Save is worth employing. Even spells like Disintegrate and Harm may be worth a cast, even assuming their damage will be reduced due to Armag's Fortitude Save. Armag has plenty of Hit Points, but not enough that he can shrug off such an onslaught indefinitely.
The only question is, how to keep him from murdering you while you cast these spells? You have several options, including simply spellbuffing your warriors and hoping they survive long enough - and contribute enough damage - to allow your casters to whittle Armag down. A better solution is to summon plenty of fodder before you provoke Armag and let him cut his way through them, buying you precious rounds to inflict damage. Aforementioned spells like Chains of Light may buy you more time, but it's hard to pick it over Hellfire Ray, which any competent Cleric can use to deal 30-40 damage to Armag each round.
As for Armag's skeleton pals, there's a sneaky way of mitigating the role they'll play in the battle... your good old friend, Web. Sneak forward until you can see just past the dead barbarians in the middle of the room and cast one Web to the west, and another to the south. If you want complete coverage, throwing a third Web spell at Armag will do, but his Athletics score is high enough that there's virtually no chance he'll be hindered at all, so don't count on it.
So, to recap: sneak forward and cast several Web spells to catch Armag's Greater Skeletal Champions. Summon a bunch of critters to serve as fodder - numbers matter more than potency, expect Armag to cut through one every time he attacks. Spellbuff your party, send a character forward to provoke Armag, then retreat when he attacks. Hopefully most - if not all - of his skeletons will be caught in the Web spells and the creatures you summon will hold Armag up a few rounds. During this time, blast him with spells to reduce his Hit Points, and engage with your warriors if and when he kills all your summons.
When Armag is defeated, his skeletal minions will cease to be a threat, too. After a moment, Armag will collect himself enough to talk, and at any stage of the conversation you'll be able to inflict to coup de grace, should you not dare to spare the barbarian. If you choose to hear him out, however, you can ask about the Deface Sisters, his upbringing, why he attacked Brevoy, and so on. Ask him "What will you do if I let you live?" and you'll get the option to spare him [Chaotic Good], after which you can fraternize with the barbarian chieftain by becoming blood-siblings.
It's probably not a bad thing to have a barbarian chief so closely bonded to your cause. He's also got no love for this "ninth mother", whose identity should be easy enough to guess. In a way, the two of you are siblings in misery, bound by the destructive ambitions of the Guardian of the Bloom.
On the other hand, if you kill Armag you can loot him for Ovinrbaane, Enemy of All Enemies, a Bastard Sword +5 with the "Oversized", "Anarchic" and "Speed" properties. While it might seem like a dream weapon for Amiri, the wielder must make a [Will 23] save each round or go berserk, attacking the nearest target - friend or foe. The DC of this Will Save increases by one each round of combat, and Will is not her strong suit. Less controversial is the Adamantine Breastplate +4, Belt of Physical Might +4, Amulet of Natural Armor +3, Ring of Protection +4 and Cloak of Resistance +4 he drops. Certainly you can find a home for all these high-quality magical items.
Either way, you can loot one of Armag's skeletal servants for a Skymetal Cogwheel. There's also a pair of chests (one hidden [Perception 35]) in the northern corner of the room, one of which contains a Leather Scrap Covered in Ancient Runes, while another chest in the southern corner of the room which holds a whopping 3,789 GP.
Batch of Blood Bones Secret Room
Believe it or not, that's not all the loot to be had in this tomb... nor the last fight. Along the southwestern wall of the room Armag occupied - near the chest full of gold - you can find a secret door [Perception 35]. Beyond this secret door is a small chamber occupied by a Spectre, two Bloody Bones Beasts and two Skeletal Champion Berserkers. There's also a trap in the center of the room, but this is tactically irrelevant, since you probably don't want to rush on in there, anyways.
Isolating and dispatching one Bloody Bones Beast is rough, but doable, but two can be a chore. You may just have success with a strategy similar to the one you employed against Armag, however, the goal this time being to isolate the two Bloody Bones Beasts and quickly remove one with magic. Cast a Web spell at the center of the room so its edge blocks the door, then retreat and lure the Bloody Bones Beasts to the northeast.
Again, they almost certainly won't be affected by Web, but their companions might. When they're isolated, focus on one of them and hit it with all your nastiest spells: Disintegrate, Hellfire Ray, Chain Lightning, Heal, etc. Unlike Armag, their Fortitude Saves are what you want to challenge, and while they're not terribly low, they're not unconquerably high like their Reflex Saves. Once you've dispatched one with a combination of magic and might, the other shouldn't be too far behind, and the Spectre and skeletons aren't anything to worry about on their own.
Conquer this last group of undead in this dungeon, disarm the trap, then search the room for treasure. You'll find two chests you can loot, one of which contains a Heavy Shield +4. Almost certainly bound to be an upgrade for somebody!
Finishing Up Armag's Tomb
Leave the secret chamber and exit the room where you encountered Armag via an exit to the northwest. Along the northwestern corner of this chamber you'll find a hidden [Perception 35] chest, which houses a suit of Chainmail +4. Another, less obscure chest can be found in the room's eastern corner.
To the southwest you'll find a passage connecting you to the earlier part of this dungeon, allowing a quick egress. Convenient, that. If you want a bit more loot before you go - and your Perception skill is up to it - search the northeastern wall to find a final secret door [Perception 35]. In the room beyond you'll find three chests, one of which is hidden [Perception 35]. One of these chests will yield a Longsword +3, another will forfeit an Ancient Kellid Ceramic Potsherd, while in the hidden chest you'll find the Protector's Robe, which gives its wearer a +5 Dodge bonus to Armor Class, a +1 Attack Bonus and damage bonus with unarmed attacks... the perfect bit of clothing for your adventuring Monk.
With that, you're finally, mercifully done with this tomb.
The Future of the Tribe
Leave the tomb and you'll be treated to a scene of dissent among the Tiger Lords. If Armag is dead, you'll get a chance to pass a value judgment on the dead barbarian, but things proceed the same way, regardless. Gwart will ask you to help decide the fate of the Tiger Lords by easing tensions within the clan by taking in any disaffected elements, and by helping pick a new chieftain. To accept them, pick the dialogue option "All right, I'll take in any Tiger Lords who wish to leave their tribe and live on my lands - provided they swear an oath of fealty first.", while you can reject them by saying "Why are your quarrels my affair? Go back to Numeria and do whatever you like. Leave me out of your feud." followed by "You heard me - leave. If I find you in my lands again, you'll be greeted with fire and steel!".
The former is a simple enough decision, either you choose to have good diplomatic relations with the Tiger Lords, or you drive the Numerian barbarians away with threats. In the latter case has a few options, many of which probably won't be available to you given your past options. Possible candidates include Amiri, Armag, Dugath and Gwart, but if Armag or Dugath are dead, they won't be candidates. Obviously. Also, Amiri will only be a candidate if you completed Betrayer's Flight before Hour of Rage. There's quite a good possibility that Gwart will be the only viable contender.
Pick whomever you wish (or whomever is available, as the case may be) and enjoy the experience reward for finally ending the threat from the Numerians. There's bound to be more trouble and strife, but for now you turn your attention elsewhere. If you return to the throne room in your capital, the quest Coronation will proceed. If you haven't completed it yet, you can simply avoid returning to your throne room for now (provided you haven't been absent too terribly long, of course) and head to Candlemere Tower to see about completing Betrayer's Flight.