Mary is the mediatrix of all graces

The summit of God's love for creation is the Immaculate. And in her comes the miracle of God's union with creation.

As with a bride, the Father entrusts the Son to her; the Son descends into her virginal womb, becoming Her Son, while the Holy Spirit prodigiously forms the body of Jesus in her and makes His home in Her soul, filling it so ineffably.

From the moment of this union, the Holy Spirit does not grant grace, the Father does not bring down supernatural life into the soul, through the Son and the Spirit, except through the Mediatrix of all graces, the Immaculate, with her assent, and her collaboration. She receives all the treasures of grace as her own, and distributes them to whomever she wishes, and to whatever extent she wishes (1).

Saint Maximilian Kolbe Marian Encyclopedia

(1) Scritti di Massimiliano Kolbe, a cura del Centro nazionale Milizia dell'Immaculata, Roma 1997, § 1310, p. 2303