He Who Fights with Monsters

1. The road contract doubles as a way to give Belinda experience for her Adventure Society Assessment. In a town where Jason met the Shabs earlier, he faces a silver-rank monster manifestation alone, holds it off until his team arrives and is gravely injured. He sleeps four days and wakes with his first scar.
2. Back in Greenstone, a silver ranker kidnaps Jason on the orders of Cole Silva, Killian Laurent and Lucius Lamprey, head of the magic society. Killian tries to force a Star Seed, looted by Jason but seized by the Church of Purity, into him. Jason's soul is inviolable, so it cannot be implanted without his consent. His Apocalypse Beast Leech familiar, Colin, helps blunt the damage.
3. A guard Jason once spared kills another guard and warns the Adventure Society. Killian kills a guard and abandons Cole. Jason briefly overpowers his suppression collar, eats a gold spirit coin and escapes. He binds Cole just as Danielle Geller's skimmer carrying his friends arrives.
4. Jason recovers at his cloud boathouse, practicing with the collar, and projects a visible aura large enough for the whole marina district. He works to raise one of his powers to bronze while Clive studies astral magic.
5. The team enters the Reaper Trials astral space with the Adventure Society's blessing and finds its magical density raised by the Builder's cultists. Clive and Humphrey reach bronze rank, the team flees a silver Bloodweaver Spider's minions, finds a prison holding a sword guarded by a bodyless soul and wisely leaves it. After Jason reaches bronze rank they kill the spider.
6. The Builder arrives in the body of Dougall (from the first volume) with the silver Archbishop of Purity and bronze Priestess Anissa. The team ambushes and kills Anissa; silver Timos escapes, marked by Jason. They beat the Archbishop and loot his supplies.
7. Clive plans to stop the astral space from exploding and destroying Greenstone by carrying a device to the top of the tower. Jason's video-game-inspired plan, leading a train of monsters into the enemy base, creates enough chaos to get the team in. Jason fights the Builder while the team fights Timos. Several team members undergo racial ability evolutions, and Humphrey gains a second, thought to be impossible.
8. The Builder collars Jason, but Jason again overpowers it by eating another gold spirit coin and drags the Builder out of a window. Both land on the spikes below, and Jason dies instantly. His gear returns to his inventory and his World-Phoenix Token is consumed.
9. TV Tropes' Book 3 recap agrees with the wiki arc summary and adds the aftermath: as Jason dies the World-Phoenix token activates, and the Builder, World-Phoenix and Reaper meet through their prime vessels (Shako, Dawn and Velius). They agree Jason will be sent back to Earth to fix the problem the original Builder caused, and the Builder agrees not to interfere with him there.

Jason dies taking the Builder with him, his body glows with heat and vanishes in rainbow smoke, and at the meeting in Interstice the Builder, the Reaper and the World-Phoenix agree he will be sent back to Earth. The Builder, having left Thadwick's body, consumes the soul guarding the Reaper's sword and becomes a far stronger energy vampire. Jason's team holds a memorial and parts ways, with Clive and Belinda joining the Magic Society's Builder-cult investigation and Sophie mentoring Emir's granddaughter. On Earth, Detective Adam Cosgrove is hired by Jason's sister Erika Asano over the vanished apartment.

Jason reaches bronze rank inside the Reaper Trials astral space (wiki arc summary), then dies. His rank after his death is not stated in the cache.