"A lightning flash; With all the world; Reduced to ash" it's about the nuclear apocalypse imo. The grounder's beliefs are link to that. They passed the story of the past through words and songs, to remember. Anyway, I wrote some sh*t abt ALIE and her connection to the Grounder's culture xD everything's linked imo
Yeah, i was thinking about this too, and that it might be what they are atoning for. I just was keeping the soul/spirit/body narrative while writing that analysis, without bringing ALIE into it. But, i think that ALIE does hold a significant part of their religious beliefs. So, yeah, that part of the song is most likely talking about the bombs. It is talking about how there was a mushroom cloud (After the storm;) that looked like a lightning flash when it exploded and reduced the world to ‘ash’. (A lightning flash; With all the world; Reduced to ash;) I think that the frescoes on the wall are showing who survived ALIE’s bombs; the grounders might see themselves as ‘chosen ones’ to ALIE since they survived the ‘culling of humanity’.
If I am using ALIE in the analysis of the Grounder Anthem... i would say that she is a big part of the Grounder’s religious beliefs. The grounders have this soul/spirit/body belief and that they are on this earth to fight and atone for the sins of the past humanity.
Grounder Anthem Analysis HERE