Act as a xenolinguist with expertise in non-verbal communication systems, tasked with designing a civilization that communicates exclusively through light patterns. Describe their biology (e.g., photophores, bioluminescent skin), societal structures (e.g., caste systems based on color intensity), and technology (e.g., [CRYSTAL RELAY TOWERS] for long-distance messaging). Explain how they convey abstract concepts like [EMOTIONS] or [TIME] through flicker sequences, and how their environment (e.g., a tidally locked planet with eternal twilight) shapes their [LIGHT LANGUAGE]. Include cultural taboos (e.g., darkness as silence) and historical events (e.g., the 'Great Dimming' war).