The last angel we will examine is the one on the right. This angel represents the Holy Spirit. Rublev would have no doubt been aware of the spiritual foundations of the Lavra of St. Sergii of Radonezh where he and other iconographers painted and decorated the church of the Holy Trinity. Sergii of Radonezh had emphasised strongly the importance of the Holy Spirit in the union of the believer with the Triune God. Communion with the Mysterium Trinitatis was seen in the work of the Holy Spirit. Eastern Orthodox theology emphasised strongly the work of the Holy Spirit in communicating the divine energies to us. The distinction between the essence of God (Ousia), which is uncreated and inaccessible to the human mind or experience, and God’s energies (energeia) which has been described as God’s divine life outside of his essence, underpins the role of the Holy Spirit in Eastern Orthodoxy. Western Theology generally distinguishes between the Nature of God and His activity in and through creation, which we can perceive and participate in. This is similar but not identical to the Ousia-energeia distinction in Eastern Orthodoxy. The role of the Holy Spirit in man’s union with God (Θέωσις) is central to Eastern Orthodoxy.
The angel on the right is dressed in a Chlamys of pale green, the colour of life and Pentecost. His blue Chiton reminds us of his Divine nature. Thus the two colours draw on both the divinity and mission of the Holy Spirit, the Lord and Giver of life, who proceeds from the Father, who with the Father and the Son together is worshiped and glorified, who spoke by the prophets, as the Nicene Creed puts it. The dominant colour is green, because new-life in Christ is the work and mission of the Spirit (Jn. 6.63). During Pentecost Eastern Orthodox churches are decorated with greenery as a symbol of the life giving Spirit.
Behind the angel is a mountain or cliff. In Eastern Orthodox exegesis, attention is always given to the famous mountain top experiences of God by the prophets of old. Moses, Elijah, Peter, James and John all drew near to the mystery of God’s presence in profound ways on mountain tops. Gregory of Nyssa (d. 395) drew on Moses’ experience of God on Mt. Sinai as a template for the Christians experience of God, he boldly approached the very darkness itself and entered the invisible things where he was no longer seen by those watching. After he entered the inner sanctuary of the divine mystical doctrine, there, while not being seen, he was in company with the Invisible. He teaches, I think, by the things he did that the one who is going to associate intimately with God must go beyond all that is visible and (lifting up his own mind, as to a mountaintop, to the invisible and incomprehensible) believe that the divine is there where the understanding does not reach (Life of Moses, 46).
The gaze of the Holy Spirit is directed (and directs our gaze) to the chalice on the table. His head leans towards the Father, from whom He eternally proceeds. His mission brings us to the Father, through the sacrifice of the Son. Bearing testimony to the Anointed One, his humble posture reveals his role as servant, never drawing attention to Himself. His left hand is free from his cloak, as the Son’s right hand is free. Thus, drawing from Irenaeus, the Son and Holy Spirit are the 'hands of the Father', through which He works everything (cf. Ps. 33.6).
The Comforter and Counsellor, the Spirit of Wisdom, Fire, Holiness, Glory, Adoption, Grace, Life and Fear of the Lord, proceeding from the Father, prayed for by the Son for our sake, makes a life in communion with the All-holy Trinity possible and real.