'I was told that everyone I'd served with in the military died shortly after I left.'
Conn Thompson was an ex-soldier, turned bodyguard, who was based on The First World prior to its destruction. Believing his squad mates to have died after he left the service, he encountered Higgins, one of his ex-squadmates, which spurred him to begin investigating the lies told regarding their demise, and the mystery of their survival.
Thompson was employed by Ethan, a rich and influential individual who offered to get him back into the military if he so desired. Ethan was successful, in a way, as Conn Thompson was reactivated and given new orders prior to entering a portal in a Portal hub facility on The First World. These orders later turned out to be fake, and Conn Thompson was effectively exiled from The First World for asking difficult questions.
From his incarceration on Teskoy Prison to his subsequent escape after the destruction of The First World, Conn teamed up with The Council, Danny and Thomas to fight The Crushing Fist, culminating in The Battle of the Capital Temple. While Conn did not participate in the assault on the Capital Temple, he instead chose to stay with Cristina Thompson, who had been sent into exile as a result of her actions in the destruction of The First World.
Conn then accompanied Cristina Thompson and one of Noah Fulmer's iterations to Noah's home universe, where the Quantum Duplication Rift/cleft was used to create thousands of copies of both Noah and some heavy weaponry and armor. Conn then separated from Cristina and the Noah army and engaged the Preacher, which had stolen Laura Thompson's body and soul from the graveyard in which she was interred.
After a lengthy chase and melee with the Preacher, Conn apparently succeeded in stranding the Preacher in the universe inhabited by one of the desolate guardians capable of firing every nuclear device on the planet simultaneously. Conn then self-terminated using a Gemstone Hegemony Amethyst Suicide Device, leaving the Preacher to die from radiation damage, as the guardian had succeeded in launching all of the nuclear devices of his world.