i was a lil confused as to why these things were never touched on? but since the heartless were created its a common idea that it was formed inside of a laboratory. and ansem made them. so what are the guards guarding (dilan and um... ok lexaus) i think is the lab and xigbar works there and i dont neccesarily know his story yet but i think that once the heartless were created one left and killed sum ppl forming more heartless and then took the hearts of the org13 we know today and took over radiant gaden. this is one theory. the second is that in the lab there was a giant dark explosion turning everyone in town into heartless and nobodies and decimating radiant garden. sum1 just randomly named it hollow bastion. wha do u think?