Nigun led the Sunlight Scripture, a military organization serving the Slane Theocracy. The guy was genuinely devout—he saw the power he wielded through his position as something divinely granted, which made him arrogant and overconfident in his abilities.
His main claim to fame is being ordered to assassinate Gazef Stronoff, the Re-Estize Kingdom's strongest warrior. But when things went south in actual combat, Nigun's true character came out: he abandoned his own subordinates without hesitation and tried to save his own skin instead of standing his ground.
Before that assignment, Nigun had been running all kinds of illegal operations as captain of the Scripture. One mission involved raiding a demi-human village, but he got stopped by Blue Rose, an adventurer party whose leader left him with a permanent scar across his face. Rather than hide it, Nigun kept the scar as a constant reminder of that loss.
Content compiled by AnimeList.moe from publicly available sources.