The artificer was a homebrew class with no place in the setting. I explained to the player before we started the campaign that she'd constantly face difficulty just traveling with her mechanical marvel, and that her inventions would have wide-reaching consequences.
She had no idea how bad things really were.
Her carriage was pulled by the marvel. The party acquired magic objects at a rapid pace through her. They got richer than they knew what to do with themselves, attracting the attention of the wealthy, the noble, and the powerful.
They also stuck their nose in a necromancer's hideout, stole some of his things, and were scried on for months.
The artificer eventually could not refuse the sums of money being offered to her, taking a contract of one million GP to develop the bio-weapon for the military.
The noblewoman had amassed a network of urchins and skilled spies in the capital city, uncovered her Father's plan to convert the Queen to vampirism, and she herself had a massive reputation.
The barbarian recovered his mind, and channeled his rage over losing his lover and his old life into building a new one. He opened his own bar, and started the reconstruction of his new home town. Between that and revitalizing their first benefactor's challenge dungeon, he made a huge name for himself as a philanthropist.
The bard found love, and his talent got him into the wedding as the first act. Speculated to be a hack, his growth into an honest and talented swordsman brought him respect and fame.
So every player was enormously invested in protecting everything they had come to love. The advent of a southern migration, to a foreign Princess marrying their Prince, to her banning all magic in the country, to an outright invasion. They were willing to sacrifice everything to put a stop to it.
The rogue played a fool the whole game. From the first session, his mission was to kill the Princess, and pulled the strings to make it happen.