well....
Last session ended very badly for my players, although it could have been much worse.
They are currently gathering shards of a broken sword. The guy they work for/with (an extremely old dwarven vampire in a world with no dwarves) has been helping them, selling them magical stuff at reduced price, and more importantly sending them near the location of each shard (with a command word to come back once they get the shard).
Last shard is held by drows, and they know it radiates anti-magic. Normally they don't know what each shard does, but I figured sending them against -that- unknown would just be asking for a TPK. So last session they were sent to a small dwarven/human village (it's on another plane) that is close to the entrance to the Underdark closest to the drow city with the shard. After lenghty information-gathering (the villagers were reluctant to tell them anything), they learned the location of the entrance, but were warned that a dragon lived there. They go to the entrance, and find it blocked by 5' of solid granite. After a few spells, 2' of granite is left, and they dig through it. They explore a bit of the cave, pretty successfully, before entering the lair of the dragon proper.
The dragon is an amethyst dragon, who hates the drow. However, he knows he isn't strong enough to defeat them, so he sealed the entrances while he's gathering power. He notices that the characters have quite a few magic items, many of them powerful, and refuses to let them pass, as he believes the drows will annihilate them, and be made even "stronger" by having their items. The characters mentally discuss what to do, and right before deciding to attack, one of them asks the dragon if they could prove their "strenght" by any way other than battle. The dragon suggests a game of chess.
They agree, but I proceded to win the game of chess. So they immediately attack the dragon (which, btw, insures that no quarter will be given in any subsequent battles, as the dragon is quite pissed).
Well, it's then that everything went bad. As if the battle wouldn't have been hard enough, my players rolled badly, the strongest fighter misses his save against the fear aura and Dimension Door as far as he can, the magister, who normally uses almost only fire spells decides for some unknown reason to switch to electricity (amethyst dragon = immune to electricity, no special resistance to fire). So after two rounds, one of my players (whose character died twice already) panicks (well, he was probably right to do so) and uses the command word, sending them back to the dwarven vampire without the shard. Now, it takes a lot of energy for him to send them there and brings them back, so he's slightly pissed too (as he has a lot of stuff to do these days), and will warn them that he'll only send them back once more, so they better have the frickin' shard.
So yes, next session should be fun, as they go back after a prepared, warned and pissed dragon. Of course, once they beat him (if they do), they still have to deal with the underdark and the drows...