For all his epic deeds, the first high king earned countless enemies, and word of his tomb’s rediscovery has gathered an eclectic army of dwarves’ ancient enemies. To preserve the tomb and save a dwarven city, the adventurers must infiltrate, splinter, and sabotage the gathering legion. Only in this chaos can the adventurers catch up to their rival at the tomb itself. The question isn’t just whether they can prevail, but whether their victory makes them worthy of the tomb’s greatest secrets.
Heavy is the Crown is a Pathfinder adventure for four 8th-level characters, concluding the Sky King’s Tomb Adventure Path, a three-part monthly campaign in which a group of adventurers travel deep underground to discover a legendary dwarven king’s tomb, seek subterranean treasures, and heal millennia-old injustices—all while stopping an ambitious villain from weaponizing those same discoveries. This adventure also includes exciting ways to continue the campaign, an overview of the subterranean Darklands, a gazetteer of a lost dwarven homeland, and fearsome creatures that prowl the darkest caves.
Each monthly full-color softcover Pathfinder Adventure Path volume contains an in-depth adventure scenario, stats for several new monsters, and support articles meant to give Game Masters additional material to expand their campaign.
I wonder if you couldn't stitch together this AP, book 4 of Age of Ashes (set in a haunted dwarven city in the Darklands), and book 5 of Extinction Curse (set deep in the Darklands, in a desert vault where Urdefhan and a city of undead Drow endure) into some sort of franken-campaign.
You'd still need a book 6 to act as finale, and the plots would need to be extensively rewritten... but it's an idea.