What the prophet has written can't be unwritten. As he has seen it, so it shall come to pass.
Every prophet should have an archangel "tethered to them." Any presence of danger will cause intervention from his or her archangel, as when Raphael protects Chuck from the demon Lilith. By the time Kevin Tran is revealed as a prophet, Gabriel was presumably killed by Lucifer, Raphael was killed by Castiel, and the archangels Michael and Lucifer were trapped in Lucifer's Cage, though Kevin does end up going with the remaining angels from Castiel's old garrison. They are, however, killed by the Leviathan Edgar, who in turn kidnaps Kevin and his mom. Once the Leviathan threat is neutralized, Crowley in turn takes Kevin. When the angel Samandriel offers the protection of Heaven for Kevin, Linda Tran turns the offer down, citing the Leviathan incident and how Kevin ended up missing for a year, and decides to take her chances with the Winchesters.
Castiel claims that Leah (who turns out to be the Whore of Babylon) is not a prophet because he knows every prophet's name. Later he reveals that all angels instinctively know the names of the prophets past, present, and future in the current generation. He also tells Sam and Dean that there cannot be more than one prophet at a time, so while Kevin is the prophet, Chuck was assumed dead and other living prophets are not active. Samandriel reveals the names of the seven living prophets, not counting Kevin Tran, to Crowley under torture: Luigi, Justin, Aaron, Maria, Dennis, Krista, and Sven. He also tells Crowley that the next generation has not been born yet. For fear of another prophet coming along and becoming a threat, Metatron tells Gadreel that he has made it so no other prophets will be activated after Kevin Tran's death.
After Amara is released, she attacks the town of Lewis, Oklahoma, with a deadly fog. The fog activates future prophet Donatello Redfield, with the Winchesters speculating that the fog was Amara's "God power." Donatello receives visions of Amara's release, Amara herself, and Kevin repairing the demon tablet in 8.23 Sacrifice upon being activated. He also gains an innate understanding of the Enochian language and the ability to detect and track both Amara and Chuck, something he describes as a "ping" in his cerebral cortex. Shortly after helping the Winchesters to rescue Lucifer from Amara, Donatello's soul is consumed by Amara to find God's location.
Despite Donatello's soul being consumed, he survives and remains a prophet, retaining the abilities he had gained from his status as one. About a year after losing his soul, Donatello is able to sense the birth of the Nephilim Jack Kline and track him down. Donatello's abilities enable him to sense that Jack's power was nothing like Lucifer's and was "not dark, not toxic." He is later able to use his abilities to track down Jack and help the Winchesters rescue him from the Prince of Hell Asmodeus.
Sam and Dean summon Donatello to translate the demon tablet with the hope that they can find a spell to open a rift to Apocalypse World. While getting chicken wings, Asmodeus arrives in the form of Castiel and controls Donatello's mind, compelling the prophet to report to him with everything he finds on the tablet. Due to his soullessness, he was corrupted by the dark energy resonating within the tablet and turns against the Winchesters. With no other option, Castiel strips the spell from Donatello's mind, leaving him brain dead.
Over a year later, the Winchesters discover a new prophet, Tony Alvarez, despite the fact that Donatello is not dead. It's speculated that Donatello's state of being between life and death caused Tony, who was next in line, to be prematurely activated. However, this creates a malformed prophet who is driven insane after hearing what he believes to be God instructing him to enact divine retributions, but later they discover that Tony was hearing Donatello's mind reciting the word in his comatose state. Tony later commits suicide after two murders and an attempted third, but the Winchesters and Castiel realize that the prophet line will remain corrupted as long as Donatello is in his current state. Though they plan to take Donatello off of life support to fix the problem, they instead discover that Donatello's mind is trying to rebuild itself, making him no longer beyond help. Castiel manages to awaken Donatello, who remains soulless, but is no longer twisted and corrupted and has no memory of when he was.
While Nick is searching for a way to bring Lucifer back from the Empty, he joins forces with a group of demons, who reveal that prophets can be used as conduits to communicate with someone in their afterlife by injecting them with angelic grace. Pursuing this plan, Nick captures Donatello in his home and injects him with grace. Lucifer uses him as a mouthpiece to communicate with Nick and reveals that the key to reviving him is a ritual using Jack's blood.
Powers and abilities
A prophet's purpose is to be God's voice on Earth. In Chuck's (and Luke's) case, this meant he could see the future events to come, in relation to writing the Winchester Gospels (although it was later revealed that Chuck was in fact God); for Kevin Tran this manifested as an ability to read the language in which the Word of God is written on stone tablets, and for Donatello Redfield it manifested in visions and the ability to sense surges of celestial and cosmic energy. Donatello displayed the ability to sense and track beings of great power such as Amara and Jack Kline, and possessed the ability to detect energy and tell if it was good or evil. Like Kevin, Donatello could read the demon tablet, though it appeared to be harder for him to accomplish. It was suggested that the next prophet to be activated would also be able to read the demon tablet.
While translating the Word of God, the human soul acts as filter, inoculating the prophet from any dark influences resonating within the tablets. Due to Donatello's soul having been consumed by Amara, translating the demon tablet leads to a psychotic break, causing him to "hear" the demon tablet and be influenced by its darkness.
Although Kevin and Donatello needed to be activated through a divine event, the unearthing of the Leviathan tablet in Kevin's case and contact with Amara's rabid-inducing fog in Donatello's, not all prophets required this for activation. Generally, one prophet is activated when the prophet before them dies. After Donatello's corruption, it was suggested that killing him would be the best bet as it would activate the next prophet who could read the demon tablet for the Winchesters. Due to Donatello being in a state between life and death, Tony Alvarez was activated prematurely, but this created a malformed prophet. It was believed that all future prophets would be malformed upon activation while Donatello remained in his vegetative state, suggesting that the prophet line continues to run through Donatello despite Tony having been called. This is repaired when Castiel restores his mind. While he remains soulless, Donatello is no longer corrupted from the demon tablet's dark energy. 
Nick discovered that prophets can be used as conduits for communication. By boosting a prophet's connection to Heaven with angelic grace and messing with Donatello's "frequency", Nick was capable of making contact with Lucifer in the Empty, who used Donatello as his mouthpiece to relay to Nick how to resurrect him from the Empty.
Castiel makes a reference to Luke in 4.18 The Monster at the End of This Book, implying that he was more of a mess than Chuck. Luke wrote a number of books of the New Testament known as the Gospel of St. Luke.
Chuck Shurley was believed to be a prophet of the Lord and the author of the Supernatural books. He makes his first appearance in 4.18 The Monster at the End of This Book. He was given the ability to see future events concerning the Winchester brothers. Castiel later informs Dean that one day these books will become known as the Winchester Gospels. In 11.20 Don't Call Me Shurley, God reveals to Metatron that "Chuck Shurley" was just an act, done so he could have front row seats to what was going to happen.
Kevin Tran is made a prophet once Sam and Dean shatter the clay holding the Word of God tablet, and he is compelled to drive to Indiana where the tablet is so that he can retrieve it. Kevin, as a prophet, proves to be the only one capable of translating the tablet - not even Castiel is able to read it. He is also able to put the pieces of the tablet back together after it is broken and is driven to keep it close to himself. Kevin is able to translate the information that is inscribed on the tablet explaining how to kill Leviathans and is later kidnapped by Leviathan leader Dick Roman to translate the tablet for him. After Dean kills Dick, the demon Crowley kidnaps Kevin twice to translate another tablet for him, this one about demons, so that he can help him open the Gates of Hell. Kevin escapes by himself the first time, and is rescued the second time by Dean, Sam, and Castiel, leaving with half of the demon tablet. He soon ends up hiding in a houseboat that belongs to the hunter Garth while he deciphers the three tasks toward closing the Gates of Hell. Crowley eventually tracks him down and kidnaps him once again, this time placing him in a replica of Garth's houseboat, and using magic to disguise two demons as Dean and Sam to make sure he translates the demon tablet for him. Kevin eventually realizes what is going on, since the demon Sam and Dean were being too nice to him. Just as Crowley is about to kill Kevin, the angel Metatron arrives and saves him. After that, Kevin holes up in the Men of Letters Bunker. Kevin Tran is killed by Gadreel, who is under orders from Metatron to confirm his dedication to him.
When Amara unleashes a deadly fog into Lewis, Oklahoma, Donatello is made a prophet upon coming into contact with the fog -- a representation of Amara's power. Upon becoming a prophet, Donatello is given visions of death and destruction along with images of Amara. Believing him to be a prophet after learning what happened to him, Sam and Dean bring Donatello to the Men of Letters Bunker, where it's revealed that Donatello has the ability to sense the presence and whereabouts of both God and Amara.
Donatello has his soul consumed by Amara shortly after becoming a prophet, but retains his prophet powers and status. Despite having no soul, Donatello's personality remains generally the same, and he comes to the Winchesters' aid in dealing with the Nephilim Jack Kline and the plans of Asmodeus, the last of the Princes of Hell.
While being called on by Sam and Dean to find a spell in the demon tablet to open a rift to Apocalypse World, Donatello's soulless nature leaves him open to the dark influence of the tablet. With no soul to filter out the dark and toxic energies, Donatello attempts to kill the Winchesters and Castiel to keep the demon tablet's secrets for himself. His refusal to give up the spell pushes Castiel to extract the information from his mind by force, leaving Donatello brain dead and on life support.
Almost a year later, Donatello's state between life and death causes a malformed new prophet, Tony Alvarez, to be called. After Tony's killing spree and suicide, the Winchesters decide to remove Donatello from life support to prevent further problems. However, they discover that Donatello's mind is rebuilding itself and Castiel is able to help him awaken. Donatello is left with no memory of his time corrupted and back to normal, albeit still without a soul.
Little is known of the Apocalypse World version of Kevin Tran's life prior to becoming a prophet and serving Michael. What is known is that Kevin operated under the belief that it is the duty of a prophet to serve God, but with no God around, he had to serve the ranking deity, Michael. This Kevin did indicate he was an atheist prior to becoming a prophet, and that when the Apocalypse started happening, and his friends and mother started to die around him, he was tricked and later forced by Michael to serve him, after Michael told him he was going to save the world. Working with the angels and against humanity also turned Kevin into a pariah among the other humans, who deemed him a traitor to his own kind. The strain which took a physical, mental, and emotional toll on the young prophet. Eventually he was convinced by Michael to act as a suicide bomber to send a message to Jack Kline by killing those around him, telling Jack, Mary, and their group of resistance fighters he was only doing so because Michael promised to let him into Heaven to see his mother once again, not caring that she would not be real and only a memory. Kevin died activating a magical sigil carved into his chest, killing three resistance fighters in the process.
Tony Alvarez was a young man from Fort Dodge, Iowa, who became a prophet. Like Donatello Redfield before him, Tony was not identified and kidnapped as a future prophet by Crowley. The circumstances surrounding Tony becoming a prophet are unique as he became a prophet while his predecessor Donatello was still alive. Tony was theorized by Castiel to have been activated early due to Donatello's state of being between life and death messing up the natural order. However, this also resulted in Tony becoming a malformed prophet. Like Donatello, Tony had an instinctive knowledge of Enochian, both written and spoken, but he also had a link to Donatello. When Donatello began muttering as his brain attempted to rebuild itself, Tony heard him and came to believe that God was instructing him to enact divine retributions. Driven insane, Tony committed two murders reenacting divine retributions before Sam and Dean stop him from killing a third man by burning him alive. Tony subsequently commits suicide and the Winchesters decide to take Donatello off of life support to prevent other prophets from getting corrupted on activation like Tony was.
Prophets in the Current Generation
There were seven potential prophets in the current generation, meant to replace Kevin Tran once he dies: Luigi Ponzi, Justin Hunt, Aaron Webber, Maria, Dennis Adams, Krista, and Sven. Crowley tortures Samandriel for their names and has them kidnapped by his demons. Dennis is injured by Crowley in a fit of pique and Krista is killed to demonstrate to Kevin how expendable they are to him, but the others are rescued by Sam, Dean, and Castiel who contact the police to get the future prophets home. According to Sam, they have nothing in common; they are from different places and are all different ages. They are even of different religions.
Following Kevin's death, Metatron "flipped a switch" in Heaven to prevent a new prophet being called upon who might threaten his current agenda. Following Chuck revealing himself as God to Sam and Dean, the spirit of Kevin vouches for Chuck before Chuck releases him from the Veil as well as flipping the switch for prophets back on, allowing for Donatello Redfield to become a new prophet. Despite Crowley supposedly getting all of the future prophets, he missed at least two: Donatello Redfield and Tony Alvarez, who become the next two prophets after Kevin. It can be theorized that Samandriel was holding back the names of the prophets directly next in line after Kevin to prevent Crowley from deciphering the demon tablet though Castiel also failed to mention there were any more when listing the future prophets to the Winchesters.
Prophets in Judaism
In Judaism, a prophet is seen as a person who is selected by, and speaks as a formal representative of, God, and the intention of the message is always to effect a social change to conform to God's desired standards initially specified in the Torah dictated to Moses.
The prophetic assignment is not always portrayed as positive in the Hebrew Bible, and prophets were often the target of persecution and opposition. God’s personal prediction to Jeremiah, “Attack you they will, overcome you they can’t,” was fulfilled many times in the Biblical narrative as Jeremiah warned of destruction of those who continued to refuse repentance and accept more moderate consequences.
- 4.18 The Monster at the End of This Book
- 7.21 Reading Is Fundamental
- 5.19 Hammer of the Gods
- 6.22 The Man Who Knew Too Much
- 5.22 Swan Song
- 8.02 What's Up, Tiger Mommy?
- 5.17 99 Problems
- 8.07 A Little Slice of Kevin
- 9.10 Road Trip
- 11.21 All in the Family
- 11.22 We Happy Few
- 13.02 The Rising Son
- 13.13 Devil's Bargain
- 13.14 Good Intentions
- 14.12 Prophet and Loss
- 14.17 Game Night
- Luke the Evangelist on Wikipedia.org
- 7.22 There Will Be Blood
- 8.01 We Need to Talk About Kevin
- 8.08 Hunteri Heroici