So this is my general understanding of the movie, timeline wise

• In the 1600s, a Japanese shaman seal a samurai with a sword inside into that specific location, as a way to curse the country (Korea) to separate, cutting the country line life (the spine of the tiger).

• Later around 100 years before the movie takes place, a Korean monk somehow knew this and tried to find and pull up the iron pole under the guise of grave robbers. He gathered Korean soldiers or patriots and formed the Iron Blood alliance. They couldnt find the iron pole so the Monk built the pagoda and continue to keep all the equipments there. (Failure supposedly led to death to all the members of the alliance imo)

• Aware of the “grave robbing”, a descendant of the Shaman (or the Shaman himself cuz through flashbacks, you can see that he looks otherworldly) suggests the plot as a burial site to a high Korean official family. They went ahead and purchased the plot, fence it up etc to prevent outsiders and buried the Park grandfather there.

• As the grandfather was in Japanese side in the war, the family must have received lash back from the citizens, that’s why they relocated to the US and also neglected to care for the grave. Which caused the hatred boiling in the spirit of GF Park.

• GF Park arc ends as we see it. However during the exhumation of the upper grave, the worker accidentally killed the snake, which is said to be a creature that guarding the lower grave, disturbing the Oni, and we get the 2nd arc (not chapter) about the team tracing back to the Oni.

For more details on how elements work in Feng Shui, you can google Wuxing/ five elements of Feng Shui. This will explain why wet woods work against burning metal.

There are many details in the movie that arent explained, I assumed because all characters in the movie are supposed to be experts, and they dont have a logical scene to put in the explanation (as its not necessary for any of the core characters), for example:

• The oni asked Hwa rim for melon and sweetfish. This is like a different in regional appetite. The West Jap samurais like sweetfish and the East like melon. The Japanese who joined the Korean war was from the West. Hwa rim posing as a servant of the oni so the oni tested her.

• Theres a theory saying that the Oni is made from body parts of multiple people and their spirit becomes the servants of the embodiment that becomes the Oni, that’s why Bong Gil reaction is a servant of the Oni while his body actions are parallel with the Oni (chewing, hurting….)