#senjutsu

also, feel free to use any of these ideas for fics, pls, just give me a shout if you do, I'd love to read them

They're not exactly singular entities, so much as giant masses of chakra formed from negative emotions combined with chakra use. So if a large enough concentration of chakra users kept, I don't know, killing, torturing, and enslaving fellow chakra users, a tailed beast would form. And if one did kill it, if the underlying cause of said beast went undressed, it would just keep forming again. Naruto and Gaara and the others are literally chained by the sins of their homes. And it would also give inherent motivation for them to try to fix those problems

So in the beginning, we were told that the bijuu were formed out of a combo of yin and yang chakra, and that yin chakra was form from nothing and yang chakra was life to form. Do those abilities sound at all familiar to you? Hashirama who was constantly bringing life to the trees and Madara who could create things like meteors or his susanoo. Imagine if, because they really wanted the hidden village system to work out,they formed nine guardians to protect the newly formed villages. Only for shinobi to do what they always do and some get stolen and sealed, or sealed in general, which was NOT part of the plan. So Madara obviously gets pissed by what are essentially his and Hashirama's children being enslaved, so he teams up with their youngest, strongest, and most complete child to destroy the hidden villages and free the bijuu. And you know how that goes.