His chief legal commentary on the Talmud, referred to as The Mordechai, is one of the sources of the Shulchan Aruch.
The Mordechai was murdered, along with his wife and children, in the Rintfleisch Massacres; see Nuremberg: Middle Ages.
Mordechai is a prominent legal (Halachic) work, which acquired wide authority, and was one of the sources of the Shulchan Aruch of Joseph Caro; it has also been printed as an appendix to the Talmud, since the Soncino edition of 1482.
Moses Isserles lectured on the Mordechai in his yeshivah, and many of his responsa are devoted to questions regarding difficult passages of the book.
The Mordechai, although linked textually with the Halakhot of Rabbi Isaac Alfasi, is, in fact, an independent work.
These are essentially two copies of the Mordechai, but whereas the Austrian Mordechai is undoubtedly the original form of the work, the Rhenish version has been extensively, almost drastically, abridged, including the removal of most references to Rabbi Alfasi's work.
The version published in the Talmud is the Rhenish one with glosses from the Austrian Mordechai, by Rabbi Samuel ben Aaron of Schlettstadt.