When Fire Monsters first fled into the underground network of tunnels to shield themselves from the upheaval at the end of the Dawn of Fire, most were content to remain in the vicinity of the living core and establish Fire Haven. A group of Candelavras (or a mint, as it's often called) had more ambitious goals - to explore the depths and potentially return to the surface. Though they were never successful in that particular undertaking, the Fire Top Bosses did make contact with a large chthonic entity. Over time, these spelunking Candelavras began to exhibit traits better-suited to underground life, and evolved into a Rare form with a single eye to navigate the dimly-lit tunnels. Of course, the glow of their own flames can never truly be snuffed.