Bishop Ambrose, in the world Andrew Ivanovich Sosnovtsev, was born in 1868 or 1867. In 1917 he was superior of the Kazan Mother of God yedinovertsy church in Samara, and was dean of the area. He was a delegate to the Local Council of the Russian Church in 1917-18. He was consecrated Bishop of Mster, a vicariate of the Vladimir diocese, in 1918. He remained in this see until about 1926, when he was arrested in Mster. He was in prison in Vladimir and then in the Butyrki prison in Moscow before being exiled to Turkestan. In 1928, according to one (dubious) source, he signed the acts of the so-called "Nomadic Council" of the Catacomb Church through Reader Leontius. In 1930 he was arrested and exiled. He died in exile in 1933.
(Sources: M.E. Gubonin, Akty Svyateishago Patriarkha Tikhona, Moscow: St. Tikhon's Theological Institute, 1994, p. 962; Bishop Ambrose (von Sievers), "Episkopat Istinno-Pravoslavnoj Katakombnoj Tserkvi 1922-1997g.", Russkoye Pravoslaviye, N 4(8), 1997, p. 5; Za Khrista Postradavshiye, Moscow: St. Tikhon's Theological Institute, 1997, p. 74; I.I. Osipova, Skvoz' Ogn' Muchenij i Vody Slyoz", Moscow: Serbryanniye Niti, 1998, p. 276)
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