Glowstone

Glowstone first appears in 'The Hero of Ages' as a natural cavern phenomenon, consisting of large porous rock column bases overgrown with bluish luminous fungus that casts a dim, ethereal light in the underground realms. It serves as a vital, passive source of illumination in the dark, ash-choked world of Scadrial during its apocalyptic end times, highlighting the series' intricate ecology amid the mists and metals. Though not evolving dramatically across the Mistborn series, Glowstone underscores the subtle environmental adaptations that persist even as gods rise and fall.