Initially, "Sin" was just a stalker clan. Later, under an unknown influence, they changed, becoming half-zombified (rumored to be mutants). All their PDAs went offline, and no one heard from them again. Based deep in the mines near Red Forest, Sin maintain a unique relationship with both Monolith and the Mutants of the zone. Sharing food and camp with both. This uneasy alliance has allowed monolith some control over certain mutants and creatures of the zone. 

Approved Sin Colors/Patterns
Ragged former monolith pants + black trench coats.
Red White and black urban.
Long trench coats with Religious inconography

Equipment and weapons are scavenged off the dead of other factions.