A bit in advance of Pentecost, we have some words on the role of the Holy Spirit in the process of deification by Greek Orthodox priest and theologian Christoforos Stavropoulos.  It first appeared in Partakers of Divine Nature (Light and Life 1976); I found it in the excellent compendium Eastern Orthodox Theology:  A Contemporary Reader, 2nd edition, Daniel B Clendenin, ed,  Baker Academic 2003, where it appears on pp 188-189.

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The Holy Spirit is the great resident of the church.  It is there that the Holy Spirit exercises all of his sanctifying and deifying power.  The work of our theosis, which our Lord Jesus Christ accomplished objectively, is completed by the Holy Spirit, adapting it to the life of every faithful Christian.  The Holy Spirit is the main and essential beginning of sanctification.  The Fathers of the church specifically teach that the theosis of human beings is attributable to the Holy Spirit.  The essential place of the Incarnate Word of God is matched by that of the Holy Spirit.  The divine Spirit that proceeds from the Father divinizes us.  The Spirit is "divine and divinizing".  The Holy Spirit is a divine bond which harmonizes and draws the mystical body of Christ, that is, the church, together with its Lord.  It is the Holy Spirit who makes the faithful into other Christs, and thus creates the church.  Our incorporation in the mystical body of Christ and our theosis are not exclusively the work of the incarnation of Christ.  They are also the work of the creative Holy Spirit, who creates the church with his spiritual gifts.

Through the Holy Spirit the faithful become sharers of divine nature.  They are formed in the new life.  They put off corruption.  They return to the original beauty of their nature.  They become participants of God and children of God.  They take on the shape of God.  They reflect the light of Christ and inherit incorruptibility.  Thus, the contribution of the Holy Spirit is always a finalizing action.  God the Father, before all ages, conceives of the work of salvation and theosis.  He realizes it in time, in the Son.  The Holy Spirit completes and perfects and adapts this work to people.  In the sphere of the church, the Holy Spirit mystically sanctifies and unites the faithful with Christ, thus creating and giving life to the mystical body of the Lord.  Here, in this  mystical body, the Holy Spirit's sanctifying energy shines forth.  These divine energies and the variety of graces of the Holy Spirit and the gifts which he mystically transmits to the soul of the believer, all shape and form the new Godlike human nature.  The Holy Spirit consequently has a power which re-creates, renews, and causes a rebirth.  Basil writes, "From the Holy Spirit there are the foreknowledge of the future, the comprehension of mysteries, the understanding of hidden things, the distribution of graces, the heavenly way of life, association with angels, unending happiness, residence in God, the likeness of God, and the highest of all things to be desired, to become God."  This re-creative power of the Holy Spirit is what is known as divine grace.  It comes and meets people.  It does not force.  It strengthens them in a spiritual way to walk the road leading to theosis.  However, it is absolutely necessary that people receive divine grace willingly and without coercion.  It is absolutely necessary for individuals to freely cooperate with divine grace in order to be able to travel the blessed road of union with God.