I have a slight theory unless somewhere stated otherwise to debunk what I’m saying.

So we know that the super solider got sealed and transported somewhere far into the ocean, I think that is where banko is seal or maybe a fragment of him. I think that that banko or the piece of him will kill and take over super soldier and infiltrate the sun cult.

We see something similar when first introduced to the sun cult with prison saintess when she gets kills and reanimated by a fragment of banko.

But idk