The Role of the Church in the Church

In Colossians, Paul says he suffers for the sake of the church which is Christ's body. God has been kind and generous in pouring out His gifts on the church so that when we come together as church, I know for a fact that I need you. The word "mystery" doesn't mean mysterious at one level but that doesn't what this word means. It means a thing that was secret and now is disclosed and what is that secret? What is it that Paul carries in his ministry and his body and that is kind of manifest in the church?