Alright kiddo, let me explain what a sobor on the blood means in a way that's easy to understand.
See, a sobor is a meeting or gathering of important people. And, in this case, the important people are from the Orthodox Christian Church.
Now, the blood part refers to the blood of Jesus Christ. Christians believe that when Jesus died on the cross, his blood was shed to forgive their sins.
So, a sobor on the blood is a special meeting where these important people from the church talk about how important the blood of Jesus is and how it can help people be forgiven for their sins.
They might also talk about how to take care of the church, how to help people in need, and other important topics related to the church.
Overall, a sobor on the blood is just a gathering of church leaders who want to make sure that people know about how important the blood of Jesus is to their faith.