#redigit

in my mind (not gonna preface everything w that but all fo this is speculation and headcanon. i will be talking like its true tho), the terraria world only has crimson. it formed when cthulhu died and his brain was trapped beneath the ground. it infected all kinds of shit into this living (but not breathing) hive mind and slowly spreads along the world. cthulhu's own attempt at his original self's reincarnation, instead of the cultists making mech-thulhu or moon-thulhu (moonlord)

when thw ancient spirits are released in place of the world guardian (guide/wof) once it fails, THAT is when the corruption and hallow show up. the corruption is the dark spirit and the hallow is the light. they arent physical entities, but more this energy that manifests as biomes and creatures. the hallow takes the underground guiding fairies you see and changes them to be pixies. the corruption takes the regular worms and makes them eaters.

these biomes are meant to reset the balance (as they change parts of the crimson, making it much smaller [especially after boc is defeated and the hivemind doesnt truly have a main center] than before). it takes a lot of monitoring to keep them manually contained

the hallow probably wouldnt have needed to form had the crimson not been there. regular purity of forest/snow/desert would've been enough to balance with the strand of corruption formed when the spirits are released

so the torch god is a different more concentrated entity and can manifest with a physical Form (as seen above). a neutral kind of spirit to balance out the other two. if the hardmode v had a line of Regular biome, but hes not a biome at all.