Who was Mordecai?
In the Hebrew Bible or Christian Old Testament, Mordecai was the cousin of Esther, and an Israelite of the tribe of Benjamin, whose fate it has been to occupy a distinguished place in the annals of his people. His great-grandfather, Kish, had been carried to Babylon along with Jeconiah, king of Judah ( Esther 2:5-6 ). For nearly 60 years before the scenes narrated in Esther, in which Mordecai was greatly concerned, took place, the way to Palestine had been open to the Israelites; but neither his father, Jair, nor afterward himself chose to return to the ancient heritage. This seems to have been the case also with the rest of his house, as it was with the vast majority of the Israelite people; for his uncle died in Persia leaving his motherless daughter, Hadassah, to the care of Mordecai.
Employed in the royal palace at Susa, he attracted, through the timely discovery of a plot to assassinate the king, the favorable notice of Xerxes, and in a short time became the grand vizier of the Persian empire. He has been believed by many to have been the author of the Book of Esther; and in the earliest known notice of the Feast of Purim, outside of the book just mentioned, that festival is closely associated with his name. It is called "the day of Mordecai" (2 Macc 15:36).
The apocryphal additions to Esther expatiate upon his greatness, and are eloquent of the deep impression which his personality and power had made upon the Jewish people. Lord Arthur Hervey has suggested the identification of Mordecai with Matacas, or Natacas, the powerful favorite and minister of Xerxes who is spoken of by Ctesias, the Greek historian. Few have done more to earn a nation's lasting gratitude than Mordecai, to whom, under God, the Jewish people owe their preservation.
IBSE, (in the public domain) with minor edits.