St. Stephen was a deacon and is called "protomartyr" because he is considered the first Christian martyr.
The name of St. Stephen comes up in the book of Acts 6:1-10:
Then the twelve calling together the multitude of the disciples, said: It is not reason that we should leave the word of God, and serve tables. Wherefore, brethren, look ye out among you seven men of good reputation, full of the Holy Ghost and wisdom, whom we may appoint over this business. But we will give ourselves continually to prayer, and to the ministry of the word. And the saying was liked by all the multitude. And they chose Stephen, a man full of faith, and of the Holy Ghost...
These they set before the apostles; and they praying, imposed hands upon them. And the word of the Lord increased; and the number of the disciples was multiplied in Jerusalem exceedingly: a great multitude also of the priests obeyed the faith. And Stephen, full of grace and fortitude, did great wonders and signs among the people. Now there arose some of that which is called the synagogue of the Libertines, and of the Cyrenians, and of the Alexandrians, and of them that were of Cilicia and Asia, disputing with Stephen. And they were not able to resist the wisdom and the spirit that spoke.
As well, Acts 7 accounts for St. Stephen's martydom by stoning.
The relics of St. Stephen are found beneath the high altar of the Basilica of St. Lawrence Outside the Walls, along with the relics of another deacon and martyr, St. Lawrence, after whom the basilica is named.
Within the basilica, a beautiful mosaic of St. Stephen can be seen, along with other frescoes from the life of St. Stephen:
Image Source: The Roman Sacristan
On this, St. Stephen's feast day, I would make mention of the Archconfraternity or Guild named after him which is for altar servers -- one which I myself was enrolled in many years ago -- the Archconfraternity of St. Stephen. Specifically I wish to mention two historical resources that Archconfraternity has put out for both forms of the Roman rite.
As it relates to the usus antiquior, Sancta Missa has made available online the Archconfraternity's Handbook for Altar Servers which is also available in a printed edition.
For the modern Roman liturgy, then Msgr. Peter J. Elliott published a similar guide under the title of Ministry at the Altar. Sadly it seems out of print at present, but it should be republished. Those interested might be able to procure a copy off of the used book circuit. Those who hold the copyright; please make this book available again, or contact the NLM if you would be interested in exploring this possibility further with us.
Ministry at the Altar's strength was that it was a guide which provided instruction on serving at the altar in the modern Roman liturgy, in continuity with how it was traditionally done.
