Update:
So the party gets up the next morning and instead of looking in on the lair via clairvoyance, or scrying their fallen companion, they cast Darkvision upon the Seer and she Remote View's the dragon.
The dragon makes his intelligence check and notices her, cursing to himself at her timing, he ceases the tunnel he is excavating and pauses to watch "her".
Meanwhile, she is speaking what she sees to the party--a excavated underwater tunnel--who is buffing and preparing to teleport in and dispatch the dragon.
The dragon is in the middle of excavating an escape route after the prior day's caveat, and has hidden most of his horde, and has assembled all his wights, including his most recently created wight (whom he enjoys roughing up), defending the entrance to his escape route as the geothermically heated water would slowly destroy them.
The sensation of being watched goes away and the dragon casts mage armor, and divine favor just in case. He already has an endure elements: fire on for working in the water.
The party sure enough buffs and teleports in two groups on either side of him, I rule that init will decide who is fastest on the draw, because both sides were expecting to see the other. The dragon rolls a 1 and goes dead last.
But being underwater ruins the spells of a couple casters, SR ruins a couple others, and mage armor and a high natural AC ruins most of the attacks. Why? Because in this quasi-surprise round my Players manage to roll
NINE natural 1's and fail to make a single roll above 9.
The dragon is amused by the mewling children.
He let's blast with his breath weapon on the group in front of him and the acidity of the water increases dramatically causing some damage to them, when the murk clears, they see the dragon has burrowed into the wall beside him (and turned around to face out into the narrow channel).
Then a good roll on a twinned summon monster spell summons 8 lantern archons who proceed to fire down the tunnel in a laser light show that the dragon does not appreciate. Again, everyone else is rendered ineffectual by either bad rolls or a lack of ideas what to do in reaction to this situation.
The dragon burrows up only a little so there is only about a 5' cube beneath him in the little channel, hoping to minimize the number of celestials that can injure him. He maneuvers himself around, taking cover as best he can, waiting for his viscous anatomy to produce enough acid for another gout.
The twinkling archons pursue and do their best to injure the creature, though one is eaten in the attempt. 4 more replace it as an empowered summon monster spell is also successful.
Let me tell you, lantern archons attacking with touch attacks 2 shots per archon for a d6 each add up.
Quickly.
A well placed gout of acid comes sooner than expected by the party (and the dragon rolls another 1 on his d4 for the reset time for the next attack as well----the dice were decidedly one-sided in this encounter) and most of the archons are dissolved instantly. The wounded dragon retreats further into the rock as the party stands idle back in the main tunnel with nothing to do but watch the summoner fill the narrow channel with celestials.
This behind the screen combat continues for a while with the dragon shifting shape to heal himself at one point. The lantern archon's report this back to the summoner who grimly proclaims that this is what the dragon has been doing everytime he has tunneled out of sight (this is actually in fact, the first time he has done it).
The PC's feeling defeated and drained of every spell with little to no effect (save for the lantern archons) decide to flee down the tunnel feeling outmatched before the dragon can dispatch the rest of the celestials and pursue.
The dragon actually only narrowly defeats so many taking around 30-40d6 points of damage over the lifespan of the celestials. But again, this is not known to the PC's, and the dragon's (perceived?) invincibility is (unfortunately?) preserved in the minds of the PC's.
Of course, the end of the underwater tunnel opens into the room with all the collected wights who are guarding the entrance to the tunnel from the other direction. A
firebrand, an enlarged
web spell, and many turning attempts later (combined with masterful to pathetic swordsmanship from trained warriors and drained spellcasters) clears the entire room of 49 wights.
An interesting development is a keen-eyed PC's noticing of a beaten wight wielding a familiar staff that is embroiled in the combat to slaughter the PC's. Another PC imprisons this wight for further study in a
resilient sphere and after the combat is over begins rolling the poor wight like a gerbil down the hallway out of the shifty-floored antechamber.
Of course, during this time, the dragon has used the rest of his transformations to restore him to most of his health, and has additionally used inflict light wounds to finish the work on himself. He is very much looking forward to repaying a certain sorcerer who has twice beaten him into a corner.
He rushes down the tunnel after the party who has just come across the scraps of his horde that have not been relocated or hidden as yet.
A keen of hearing PC hears a great rushing of water and assumes the worst as PC's scrabble for gold and then to one of the two teleporters. At this point the wizard realizes, just as the
sphere protects them from the wight, so too does it protect the wight from them. And she has no method of dropping the sphere.
Problem.
The dragon bursts forth from the water and evades a
resilient sphere with his name on it and pauses to whisper menacingly,
"Allow me the summoner to snack on and I may let the rest of you leave here alive..."
They do not take him up on his offer and actually manage to ensnare him by filling every dimension of the room with a triple-size
web spell. Though it looks like it will do more to further anger the dragon then to actually hinder it for long.
And then one of the PC's re-reads the possible shapes for a
wall of force spell. And he causes a 10' sphere of invisible invincible force to pop into existance around the dragon.
No save.
The dragon inhales and breathes forth his acid but it hits the invisible barrier harmlessly. The webs inside the forcesphere are instantly annihilated, but the dragon remains there, impotent.
And then the PC's proceed to pick up every remaining piece of his treasure, right under his nose and teleport out.
Somebody is going to die. OOOOOooooo somebody is gonna PAY!
