I had a Big Twist: the Dragon's Heart was not a heart but an Egg, and instead of healing Agondre, the necessary thing to do was to kill him and hatch the egg in his scorching flesh. I was worried that this twist would upset my players...
And I was also worried that the dragon would wipe the floor with the PCs. So I gave all the PCs a level to go up to level 14, and I gave them a couple of allies bringing them up to 6 members. And for the dragon's stats, I took a CR 20 Old Red Dragon, deprived it of spells and spell-like abilities, and reduced its stats substantially to show the effects of the wasting disease it's been subject to. And I gave the PCs a perfect tactical position: the fight began with Turok delivering a coup de grace (whose Fort save i deliberately ignored) to cut open Agondre's chest to implant the Dragon's Heart.
It turned out that the PCs won the fight fairly handily--no one took much damage at all. But everyone felt that they were fighting a truly awesome foe who could easily obliterate them--and that's far more important to the excitement than the damage they took.
And I got some good descriptions. I described the searing super-hot flame of Agondre's incandescent blood, and his roars in pain and rage...
The PCs were slow to realize that I meant them to kill Agondre, but Liandra realized that the look in his eyes was like that of Theodocious and Dorla when they were ready to die...
And when Larissa rolled a 20 and managed to push the Dragon's Heart into the wound in Agondre's chest, I described it cracking like an egg hatching--and Kevin lit up with the realization that this was a fitting and appropriate end.
Turok was the one to deliver the final blow to Agondre, which was just the way I would have chosen it if I were writing it as a story.
I nudged them to do the funeral blessings they'd done for the dead Emperor, and then to do the blessings they'd done for a newborn--and I got choked up with emotion both times. This is *great*; this is the emotional affect I wanted this session to deliver.
And I put the D&D Soundtrack on random shuffle for the evening, and it picked perfect music--the hot battle sounds of "Skirmish" during the final battle, and then the soaring uplifting "City of Sails" when they were greeting the new baby Dragon. I couldn't have done better if I were picking tracks one by one.
Everyone applauded at the end. It was great. But I feel we should all share in the applause--I feel this was too much and too good for me to have done alone.
I'll write more later (particularly about the first hours of the session, which I've largely skipped), but I just wanted to record how wonderful it was. Despite all my apprehensions and my failure to prepare as much notes as I'd intended, it all worked out gloriously.