Sadoc (Latin Sadoc; Polish Sadok) was one of the earliest Polish-Silesian Dominican friars — a close companion of St. Hyacinth of Poland (1185–1257, the Apostle of the Slavs, the founder of the Polish Dominican Province) in the earliest Dominican mission to Central Europe. Sadoc had received the Dominican habit directly from St. Dominic in Rome around 1220 (per tradition), and accompanied Hyacinth on the Polish mission.
By the late 1230s, Sadoc was serving as prior of the Dominican convent of Zagreb in Croatia. Around 1250 he was appointed prior of the Dominican Priory of St. James at Sandomierz in Lesser Poland (Małopolska) — the principal Dominican foundation in the Sandomierz region, founded around 1226 by Hyacinth himself.
In autumn 1259, the second Mongol invasion of Poland was launched by the Cuman-Tatar general Burundai (following the first Mongol invasion of 1240–1241, which had culminated in the Battle of Legnica of April 9, 1241). The Mongol-Cuman army swept across the Polish territory, sacking Kraków, Lublin, and the surrounding cities.
On the eve of the Feast of the Ascension (June 2, 1260), the Mongol-Cuman army arrived at Sandomierz. The Dominican community — 49 friars including Sadoc as prior — recognized that they could not escape and that the martyrdom was imminent.
Sadoc gathered the community in the church of St. James for the final Compline liturgy. According to the classic hagiographical tradition preserved in the Polish Dominican chronicles, a young friar received a vision at the reading of the martyrology in which he read the entry: 'At Sandomierz, the passion of the forty-nine martyrs.' Recognizing the imminent martyrdom, Sadoc led the community in the chanting of the Marian anthem Salve Regina — the famous Marian anthem composed in the late 11th century, the nightly Marian anthem of the Dominican Order.
The Cuman-Tatar army burst into the church of St. James at the moment of the chanting of the Salve Regina and massacred the entire community of 49 Dominicans — including Sadoc as prior — at the altar and the choir-stalls.
The 49 martyrs of Sandomierz were beatified by Pope Pius VII on October 18, 1807 — the papal recognition of the continuing Polish Catholic-Dominican devotion to the Sandomierz martyrs. The Church of St. James at Sandomierz survives in continuous Catholic Dominican liturgical use as the principal martyrdom-shrine.