As a mercenary, Cain is a ghoul through and through. Stooped, skeletal and bony, Cain is a real badass, the kind of guy that upon finding your burning body would roast desert rat over you rather than put you out. When his home was razed to the ground by the mutants, Cain took it personally. In an attempt to seek vengeance upon the mutants, he sought out the Brotherhood of Steel and demanded entry. As a some-what isolationist and anti-mutant order, the Brotherhood was reluctant to grant him admission, but Cain’s perseverance was fueled with a grim determination. He was finally given a test of Initiation, a suicide mission that should he survive would allow him to become one of the first ghouls ever to join the ranks of the Brotherhood.
Cain managed to stop the troubles brought to Texas but was changed forever in the process, he decided to leave the Brotherhood of Steel behind and became Mayor of Carbon Texas, assisting in its rejuvenation project. Cain has since turned Texas into a prosperous empire, built off of slave labour and aggressive expansion. Needless to say, this has gotten the attention of the Brotherhood of Steel.
Cain has always been rough around the edges, with each passing conflict, whether it's Necropolis, Carbon or the Secret Vault, he has gone further and further over the lunatic fringe. Now he has fully been pushed over the edge, he will not rest until his empire spans across the whole of Texas and hopefully the West Coast.
Cain seems quite contradictory on the surface, like Caesar's Legion he has a strong emphasis on law and order, in spite of his willingness to sell human beings like cattle. He despises rapists and enjoys tormenting them in his courthouse, he has little to no desire for compromise and usually insists on doing things his way.
in spite of this, Cain is surprisingly insightful. He's observant and patient enough to get all of the facts before acting out. It would seem that his old age has wizened him.
Finding Kurisu: Chapter 1 - Chain Tracks (Mentioned)
Finding Kurisu: Chapter 4 - Deception (Mentioned)