It's been some time since I looked at it, and I never read the full level 1-30 campaign, but it's about the cosmological war between Tiamat/chromatics and Bahamut/metallics as they were split from the single dragon god. It ends with the party hunting down Tiamat in a giant dungeon complex and taking down a bunch of ancient dragons (one of each color) and also solving puzzles.
Tiamat kills Bahamut, the PCs resurrect Bahamut and defeat Tiamat's armies, Bahamut sends the PCs to her domain in the midst of her forces abandoning her and while she is preoccupied trying to prevent that. The PCs must defeat 5 ancient dragons (brood mothers) scattered throughout her dungeon lair to gain access to her throne room and then battle her on a floating island with a nasty fall/trap if your knocked off.
(and @jimmythecomic)
That sounds interesting. Looking on DrivethruRPG, it looks like this adventure is scattered across several issues of Dungeon magazine. Which ones would you recommend reading to get the finale of the adventure?