The mystery of the Trinity extends to the mystery of the community of Saints. Just as the Trinity is three yet one, the Saints throughout history are many yet one. This is a mystery, but we are not merely individuals before God, but also One. Our prayers are not individual conversations with God, but are as a common prayer rising up to God the Father from all Saints throughout history. This One includes not only the Saints, but also God the Son as head of this One. Our prayers are not only a common prayer from all the Saints from all times, but a common prayer from all the Saints from all times plus God the Son, all rising up to God the Father.
The mystery continues. In the fullness of time, the last Saint will be brought into this One Body, and God the Son will return again. The Body will be complete, and this One Body, with God the Son as head, will be brought into full community with the God the Father, God the Son, and God the Spirit. The separation that separated mankind from community with God will be finished, and as One Body, we will again enjoy full community with the Triune God.