Seraph is the name of a character (played by Collin Chou) in the science-fiction Matrix universe. He is portrayed as the personification of a sophisticated challenge-handshake authentication protocol which guards the Oracle.
In The Matrix Reloaded and The Matrix Revolutions, Seraph is seen acting as a “guardian angel” of the Oracle. He refers to himself several times as “Seraph, Guardian of the Oracle”, but in actuality he has held this position since long before the time frame in which the first film takes place. We also learn from a scene later in the movie that Agent Smith has tried to hunt him before, but that Seraph confounded him in these attempts. Over the course of the Reloaded and Revolutions plot arcs, he has three brief altercations with warriors of Zion. The first is with Ballard, which he stages in order to get to know him; the second, with Neo, to prove he is the One. The third takes place in the closing stages of Enter the Matrix, after the conclusion of Reloaded but before the beginning of Revolutions. Seraph summons either Niobe or her First Mate Ghost to meet the Oracle. Whoever he summons, he first tests that person with another battle, in order to “test his/her heart’s resolve” (or, more technically, a Challenge-response authentication).
In Revolutions, Trinity and Morpheus meet with the Oracle so that she can help them locate Neo. She explains that he lies within a place that is neither the Matrix nor the Machine world: a construct created by the Trainman. Seraph, she says, knows how to find him, and will lead them to him. The trio departs to the Megacity’s subways. Seraph tracks down the Trainman, but after a chase and exchange of fire, he escapes. Seraph, Morpheus, and Trinity go to meet with the Merovingian, for whom the trainman works. They find the Merovingian holding court at his decadent nightclub Club Hel. During the assault on Hell’s gates, Seraph is referred as “wingless”, by one of the guards and the Merovingian refers to him as “his protégé”. The three make their way to the club and defeat a number of the Merovingian’s guards. The Merovingian calls him the “Prodigal Child” returning and “Judas, suggesting that Seraph betrayed the Merovingian to serve the Oracle. He also calls Seraph “L’ange sans ses ailes“, which is French for “The angel without its wings.” The crew eventually rescues Neo. Later, Seraph tries to flee with Sati from the increasingly powerful Smith. In due course, Smith catches up to them. Seraph mentions that he has defeated Smith in the past; nonetheless, Smith assimilates them both, adding two more copies of himself to his growing collective of Smiths. Upon Smith’s destruction at Neo’s hands, however, all the minds that Smith has infiltrated are freed from his abduction, including Seraph’s.