Handbook of ROCOR Liturgical Practice:

Does the Deacon ever enter through the north door in the Liturgy?

Yes. If only one Deacon is serving, after the singing of the Creed, he turns to the east and, standing before the Royal Doors on the centre of the amvon says, ‘Let us stand well…’; he may then enter through the north door so that he will be on the north side of the Holy Table, ready to remove the star from the diskos.