The guy at the bottom of the icon represents the whole world which is about to receive the teaching of the Twelve Apostles.
The second verse of the Pentecost Sequence goes as follows:
Veni, pater pauperum,I've never quite understood why the Holy Spirit is called the Father of the Poor. That would seem to be a more fitting title for God the Father. Anyone got any ideas?
veni, dator munerum
veni, lumen cordium.
I note that in some very early Christian texts, Jesus Christ is sometimes referred to in paternal terms. For obvious reasons, that particular usage didn't persevere for long.
(For example, see the Epistle to Diognetes which says of Christ: Having then in the former time demonstrated the inability of our nature to obtain life, and having now revealed a Saviour able to save even creatures which have no ability, He willed that for both reasons we should believe in His goodness and should regard Him as nurse, father, teacher, counsellor, physician, mind, light, honour, glory, strength and life without concerning ourselves about clothes and food. )