Glenn is silent, obedient, takes abuse, kills on command and would take a bullet for Cynthia without pause. Whatever power she has over him is likely rooted in his unknown past. The earliest 'Glenn sighting' was a year prior to Anatali Station's launch from Earth's orbit. He talked back then and had a fearsome reputation in District G's Brewery Hollows. A thug and bully, he lived as a mugger until he picked the wrong woman to mess with.
Legend has it Cynthia defeated the brute in four moves, which adds to her legend considerably—no one had ever defeated Glenn. Since then, he's been mute and at Cynthia's side. It's believed they are master/slave but there's little proof they're romantically involved.
As long as Glenn's conscious, Cynthia will always remain untouched, even when facing foes such as the Knights.
Fun Fact — Starred in an adult film per Cynthia's order, though the volume never made it to the network.