At Mass, the Church timelessly makes present the paschal mystery
The Church was born of the paschal mystery. … At every celebration of the Eucharist, we are spiritually brought back to the paschal Triduum: to the events of the evening of Holy Thursday, to the Last Supper and to what followed it. (3) In this gift Jesus Christ entrusted to his Church the perennial making present of the paschal mystery. With it he brought about a mysterious “oneness of time” between that Triduum and the passage of the centuries. (Ecclesia de Eucharistia, 5)
Christ restores, redeems, and returns creation to the Father through the Church
The Son of God became man in order to restore all creation, in one supreme act of praise, to the One who made it from nothing. He, the Eternal High Priest who by the blood of his Cross entered the eternal sanctuary, thus gives back to the Creator and Father all creation redeemed. He does so through the priestly ministry of the Church, to the glory of the Most Holy Trinity. Truly this is the mysterium fidei which is accomplished in the Eucharist: the world which came forth from the hands of God the Creator now returns to him redeemed by Christ. (Ecclesia de Eucharistia, 8)
The Eucharist is the source and summit of the Church’s evangelization
From the perpetuation of the sacrifice of the Cross and her communion with the body and blood of Christ in the Eucharist, the Church draws the spiritual power needed to carry out her mission. The Eucharist thus appears as both the source and the summit of all evangelization, since its goal is the communion of mankind with Christ and in him with the Father and the Holy Spirit. (Ecclesia de Eucharistia, 22)
We come to union in the Eucharist only because of the Church.
The celebration of the Eucharist, however, cannot be the starting point for communion; it presupposes that communion already exists, a communion which it seeks to consolidate and bring to perfection. The sacrament is an expression of this bond of communion both in its invisible dimension, which, in Christ and through the working of the Holy Spirit, unites us to the Father and among ourselves, and in its visible dimension, which entails communion in the teaching of the apostles, in the sacraments and in the Church’s hierarchical order. The profound relationship between the invisible and the visible elements of ecclesial communion is constitutive of the Church as the sacrament of salvation. (Ecclesia de Eucharistia, 35)
True communion and unity is through the Pope and Bishop as one community of Catholics throughout the world in the Church.
[A] truly Eucharistic community cannot be closed in upon itself, as though it were somehow self-sufficient; rather it must persevere in harmony with every other Catholic community. The ecclesial communion of the Eucharistic assembly is a communion with its own Bishop and with the Roman Pontiff. The Bishop, in effect, is the visible principle and the foundation of unity within his particular Church. It would therefore be a great contradiction if the sacrament par excellence of the Church’s unity were celebrated without true communion with the Bishop. (Ecclesia de Eucharistia, 39)
The Church acts in union with Christ, offering herself along with Christ to the Father.
The celebration of the Eucharist which takes place at Mass is the action not only of Christ, but also of the Church. For in it, Christ perpetuates in an unbloody manner the sacrifice offered o the cross, offering himself to the Father for the world’s salvation through the ministry of priests. The Church, the spouse and minister of Christ, performs together with him the role of priest and victim, offers him to the Father and at the same time makes a total offering of herself together with him. (Eucharisticum Mysterium, 3)