The "Povest'" (which is an integral part of Russian Church history) clearly states that St. Constantine was baptized by Pope St. Sylvester shortly after the miraculous victory that Christ gave him over his pagan rival, Maxentius, at the battle on the Milvian Bridge (AD 312) and not "on his deathbed" by Eusebius of Nicomedia, as modern "scholarship" so likes to assert.
For that service, in gratitude, Constantine bestowed upon St. Sylvester the dignity of wearing a White Cowl, which is symbolic of the purity of the Orthodox Faith and the Radiant Third-day Resurrection of Christ.
Soon after the Church in Rome fell to the Appollinarian heresy, the then-Pope, commanded to do so by an Angel of the Lord who appeared to him in a threatening dream, sent the Cowl to the Patriarch of Constantinople.
Later, a "radiant youth" (also an Angel of the Lord) appeared to the then-Patriarch of Constantinople and commanded that he send the Cowl on to the Holy Russian Land:
"For Old Rome hath fallen away from the glory and the faith of Christ through pride and self-will; in New Rome, which is in the City of Constantine, the Christian faith will likewise perish through Hagarene (Muslim) violence; while upon the Third Rome, which is in the Russian Land, the Grace of the Holy Spirit hath shone forth" ... for "there truly is the faith of Christ glorified" ... "and honoured ... more than anywhere else on earth".
"The Tale Of The White Cowl" further predicts the establishment of a patriarchate in Rus' ("... and the great rank of Patriarch ... will be given to the Russian Land in its time, and that nation will be called radiant [or: Holy] Rus'").
This prophecy would only find fulfillment in 1589, one hundred thirty six years after the "infidel Turks" broke down the gates of the City of Constantine and a century and a half after the Greeks had betrayed their Faith in Florence.
With the establishment of the Russian Patriarchate, the White Cowl became the headgear of Russia's Patriarchs (St. Tikhon being the last to wear it legitimately).
Thus, the Third Rome was spiritually linked with the First, by way of the Second (II [IV] Esdras 11). And, inasmuch as "a Fourth [Rome] there shall not be", the "Povest'" informs us that "at the end [of the Age] all Christian realms will come together into a single Russian Tsar'dom [i.e., the Third Rome resurrected], on account of the Orthodox Faith ... and the Lord will exalt the Russian Tsar' over many nations...".
This prophecy was also passed on to us by, among others, St. Seraphim of Sarov, who informs us that even the antichrist will tremble at the mere mention of the Russian Tsar'!
We know, for example (according to the prophecies of St. Feofan of Poltava) that "[i]n Russia, the startsy [elders] used to say, through the will of the people, the Monarchy and Autocratic rule will be restored. The Lord has forechosen the future Tsar'.
"He will be a man of burning faith, of brilliant mind and of iron will. First of all, he will bring about order in the Orthodox Church by removing all the false, heresy-preaching and lukewarm hierarchs. And very many indeed -- almost all, with few exceptions -- will be those removed by him: while new ones, true and steadfast hierarchs, will take their place.
"Through the female line, he will be from the lineage of the Romanovs. Russia will be a mighty state, but only for 'a short time'. ... After that, the antichrist will come into the world, with all the horrors of the end, as described in the 'Apocalypse'."
Elsewhere, St. Feofan states:
"Oh, Russia, Russia! How terribly has she sinned before the loving kindness of the Lord.
"The Lord God favoured Russia, and He gave her that which He had not given to a single other nation on earth. And this nation turned out to be so ungrateful.
"She left Him; she rejected Him; and it is therefore that the Lord has given her over to be tormented by devils. The devils took up their residence in the souls of men, and the nation of Russia became possessed; literally, devil-ridden.
"And all the terrible things that we hear about what went on -- and what continues to go on -- in Russia: all the sacrilege, all the militant atheism and theomachy, -- all of this stems from her being possessed by devils.
"But, through the inexpressible mercy of God, this possession will pass and the nation will be healed. The nation will turn to repentance; to faith.
"That will occur, which none expects. Russia will be resurrected from the dead, and the entire world will be astonished.
"Orthodoxy in her will be reborn and triumph. But that Orthodoxy which had existed formerly will be no more.
"The great startsy have said that Russia will be reborn; that the people themselves will restore the Orthodox Monarchy. A mighty Tsar' will be placed upon the Throne by God Himself.
"He will be a great reformer, and he will be strong in the Orthodox faith. He will cast down the unfaithful hierarchs of the Church.
"He himself will be an outstanding personality, with a pure and holy soul. He will possess a strong will. He will be of the Romanov Dynasty, through the maternal line.
"He will be God's Chosen One, obedient to the Lord in all things. He will transform Siberia.
"But this Russia will exist only for a very short time. Soon thereafter will come to pass that of which the Apostle John speaks in his 'Apocalypse'."