So in chapter 47 of the Black Clover manga we learned of a a town with people who were loved by mana and had extreme magic power.

These people were killed because they were feared by the other people and stole there power.

The reason why I think the people of that town were killed was because the king of the Clover Kingdom feared them so much that he thought that they would eventually try to take over the country. So he decided to trick them with something and got them all killed and the only ones that survive were the kids. Most of the kids that survived were old enough to know what had happened and only Asta and Juno were babies so they were left in a church in Hage village which is far away from the capital of the kingdom for protection.

The other kids that survived decided to stay hidden until they were strong enough to fight the kingdom. They created a terrorist organization to try and defeat the kingdom. We know that the leader of the terrorist organization that attack the is a member of that town. He wants to destroy the Clover Kingdom to get revenge for what they did to his town and create a new kingdom. He also has a four leaf clover grimoire just like Juno.

He also knows about Asta's grimoire which is a five leaf clover and he wants to take it back probably because it was a treasure grimoire from his town.

Thanks for reading my Theory on Black Clover.