Jesus Christ himself is. He is the eternal High Priest who offers himself once for all to the Father. The Sacrifice of the Mass is the same Sacrifice of Calvary, so the priest and victim are the same.
Yes…but it doesn’t stop there…consider the priest in addition to Jesus Christ
The priest does. By virtue of his ordination, he is empowered to consecrate the bread and wine into the Body and Blood of the Lord, and, acting in the Person of Christ, offers the Sacrifice of the Mass. Through him, Christ makes himself and his Sacrifice present.
Combine Jesus himself with the priest, as the priest, in the sacrament, is acting in the person of Christ
We do, since we gather in his Name, therefore representing the Mystical Body of Christ, and as we join our prayers and unite ourselves with the priest, we exercise our common priesthood of the baptized, making the priest’s Sacrifice our own.
And, yes.