Every new brother is assigned a job - a purpose in the Solarii. As long as Mathias continues to prove his spiritual connection to the Sun Queen, they will fall in line and believe. Initiation to the brotherhood is brutal. We need to destroy their humanity, so that they in turn can be inhumane. New recruits are thrown into the depths of the caverns and left to starve and fend for themselves for days... sometimes weeks. Those who make it out alive are welcomed with open arms.
I still can't explain what kind of power Mathias has tapped into, but I don't care anymore. We're never getting off his goddamned island - some days I'm convinced we're all in hell already. God knows with the things we've done... we might as well be.
What makes these men truly dangerous is their faith. They believe in the Sun Queen and will stop at nothing to bring her back.