sentences:  Although for validity, only one bishop (with a papal mandate) is needed to raise a priest to the episcopal state, it remains a strict rule of the Church that there should at least two co-consecrating bishops; with the sole exemption being made in missionary countries where it is very difficult to bring three bishops together.In those cases, the Holy See allows two priests to act as assistants to the consecrator.For the ordination of a diocesan bishop, the principal consecrator will usually be his metropolitan archbishop assisted by two other bishops.