My players, when it first became clear that an encounter with the dragon was in the cards for them, immediately started wondering if they could negotiate with him. I know that the text says that Razorhorn attacks immediately, but I'd like to reward them for not assuming everything is mindless hack & slash. Plus, it seems to make sense that the dragon would be interested in a deal with the other side, now that the elves have the upper hand on the drow in Mierani, and the adventure also states he's unhappy with the situation Nolveniss has put him in.
However, I've never been comfortable putting PCs up against dragons, because I don't really feel I "get" the monster in question. So here's my question: assuming that the party bard with maxed-out Diplomacy makes some decent rolls, how might this negotiation play out? What could they offer that might interest the dragon? What kinds of demands might he have, and what concessions might he make? (The party is largely interested in rescuing the prisoners and finding a way out of the Echo before Earthfall.)
Even if a fight with the dragon is inevitable, roleplaying the dragon for a bit makes the dragon more than "the next encounter." So before you figure out what the characters can offer the dragon that might get it to back you, you might want to decide if you really want them to bypass the fight, or if you just want to roleplay the dragon and give the PCs a reward for not attacking first.
If you still want to fight to happen, you can always reward them by taking the dragon unawares and getting in a surprise round on the dragon. Perhaps they make its such an offer that it is willing to take it . . . in exchange for letting get a head start running away from him.
The dragon, being so arrogant, is sure he can kill them all, and that it might be fun to take their tribute for giving them some minor hope that they might be able to run from him.
Basically in this case, if the PCs offer him something of value, and then make a Diplomacy check, he makes them the "you get a head start" offer, but if they miss the check, he's so enraged that they would offer him this, he attacks immediately.
Then you let the PCs make a Sense Motive check to realize that the dragon is so confident about them running and being afraid of him, that they would get a surprise round out of attacking him immediately.
This would give them a benefit for actually talking to the dragon, gives you a chance to ham it up as the dragon and make it memorable, but still has the PCs end up fighting the dragon.
Obviously, this is only handy if you want the PCs to still fight the dragon, but you want them to have a chance to get some benefit out of negotiating with it as well.
Also, if the PCs went through the trouble of doing all of that ahead of time, and they, say, get the dragon to 25% of his hit points, the dragon might attempt to save its hide by offering a single service to such valiant adventurers that "almost" are worthy of his notice. Then they can figure out what single boon they might ask the dragon without pushing the issue too far.
Just some thoughts.
Razorhorn seems greedy and arrogant
I think he would ask for tribute and talk to them and then once he gets all the tribute they will give him
Become greedy and attack the PCs for the rest of their treasure
Here's what I ended up doing:
Razorhorn was unhappy with his deal with Nolveniss but, being lawful, was uncomfortable with simply breaking his word to help the drow. If, however, Nolveniss were to be killed, the dragon would be free of his promise. He made a two-part deal with the PCs: he let them rescue the prisoners in exchange for them giving him the troglogyte guard to eat, and he agreed to let the PCs go up the tower to fight Nolveniss if they promised to bring the portal key back to him so he could get out of the Echo. (Nolveniss' exact order to the dragon had been to "guard the stairs," so as long as the party promised to be careful and do no damage to the actual staircase, Razorhorn considered that a reasonable loophole to exploit.)
Of course, he never promised to take the PCs with him once they gave him the portal key. If they had brought it back to him, he would have flown to the portal, leaving them behind in the Echo. Fortunately for the PCs, they intended to doublecross the dragon as well and never intended to return with the key once they got it. ;)
So I think Razorhorn should escape the Echo now as a Vampire Dragon with some blind UMD attempts till he hits a natural 20 and gets himself out