Short answers, pulled from the story.
Master MS was a 16th-century painter active in Selmecbánya (now Banská Stiavnica, Slovakia) in the Kingdom of Hungary. His true name is unknown; he is identified only by the initials M and S. Scholars have proposed several candidates, including a German painter named J. Brieu from Augsburg, a Hungarian painter named Sebestyén mentioned in a 1507 town charter, and the goldsmith Matthäus Zaisinger (1498-1555).
The surviving works are dispersed across several institutions. Four Passion paintings are in the Christian Museum in Esztergom, Hungary. "The Birth of Christ" is in Svätý Anton near Banská Stiavnica. "The Adoration of the Magi" is in the Museum of Lille in France. "The Visitation" is in the Hungarian National Gallery in Budapest.
The altar originally decorated a church in Selmecbánya (now Banská Stiavnica, Slovakia). It was long believed to have stood in the Saint Catherine Church, but more recent research suggests the panels came from the Virgin Mary Church, a building later converted into a fortress known as the Old Castle.
Seven of the original eight panel paintings that decorated the high altar in Selmecbánya are known today. Three larger-than-life-size wood-carved polychromed sculptures from the same altar have also survived, now held in Banská Stiavnica.
Master MS worked in late Gothic and early Renaissance art, combining dramatic depth with colourful decorative formation. Art historians compare his style to German painters Martin Schongauer, Albrecht Dürer, and especially Matthias Grünewald.
Major studies include a 1932 monograph by Genthon István published in Berlin, a 1957 essay by Radocsay Dénes published in Budapest, and a 1976 book by Miklós Mojzer on the Passion paintings in Esztergom, later translated into English by Lili Halapy. A 1997 exhibition catalog from the Hungarian National Gallery also gathered significant research on the original altar.