Short answers, pulled from the story.
Vladimir Solovyov (1853-1900) was a Russian philosopher, theologian, poet, pamphleteer, and literary critic. He played a significant role in the development of Russian philosophy and poetry at the end of the 19th century and in the spiritual renaissance of the early 20th century. He is best known for his Sophiology, his defense of Jewish civil rights in tsarist Russia, and his ecumenical arguments for reuniting the Orthodox and Catholic churches.
Solovyov described Sophia as the merciful unifying feminine wisdom of God, comparable to the Hebrew Shekinah. He developed this theology in works including Three Encounters and Lectures on Godmanhood. The Russian Orthodox Church Outside Russia declared Sophiology a heresy, though the theologian David Bentley Hart, in his 2005 foreword to Solovyov's Justification of the Good, defended it as rooted in the Wisdom literature of the Old Testament.
There is evidence that Solovyov converted to Catholicism in a ceremony on the 18th of February 1896. The testimony was signed by the Russian Greek Catholic priest Nikolay Tolstoy and two Catholic laypeople, Princess Olga Vasilievna Dolgorukova and Dmitry Sergeevich Novskiy. Solovyov had long argued for reunion of the Orthodox and Catholic churches and accepted papal primacy over the Universal Church.
Solovyov moved to Saint Petersburg in 1877 and became a close friend and confidant of Fyodor Dostoyevsky. It is widely held that Solovyov was one of the sources for both Alyosha Karamazov and Ivan Karamazov in The Brothers Karamazov. The two men diverged on religion: Dostoyevsky was close to Russian Orthodoxy, while Solovyov was sympathetic to the Catholic Church.
Solovyov's 1894 poem Pan-Mongolism was widely seen as predicting the Russo-Japanese War of 1904-1905. Its opening lines served as the epigraph to his apocalyptic short story Tale of the Antichrist, published in the Nedelya newspaper on the 27th of February 1900, in which China and Japan join forces to conquer Russia.
Solovyov was the leading defender of Jewish civil rights in tsarist Russia during the 1880s. He was an active member of the Society for the Promotion of Culture Among the Jews of Russia, learned Hebrew, and published a letter in The London Times appealing for international support. The Jewish Encyclopedia described him as a friend of the Jews and recorded that even on his deathbed he is said to have prayed for the Jewish people.