Associate of Widmore
On the plane...
On the island...
S1 - S2 - S3 - MP - S4 - S5 - S6
Matthew Abaddon was a mysterious agent of Charles Widmore whose job was to get people to "where they needed to be." Chronologically, he was first seen suggesting to John Locke that he take a walkabout in order to find his "purpose in life," an event that ultimately led Locke to the Island aboard Oceanic Flight 815. With Naomi Dorrit, Abaddon also recruited the science team—Daniel Faraday, Miles Straume, Charlotte Lewis and pilot Frank Lapidus—to go to the Island on a mission. Sometime after the rescue of the Oceanic Six, Abaddon visited Hurley at the Santa Rosa Mental Health Institute, suspiciously asking if "they" were still alive. Sometime later, he was assassinated by Benjamin Linus while assisting Locke once again.
Prior to Widmore's expedition
As an orderly
Posing as a hospital orderly, Abaddon met John Locke at the rehabilitation center after his fall from a window caused by Anthony Cooper. While wheeling Locke back to his room, he stopped, and urged Locke to attend a walkabout, something Abaddon claimed to experience that changed his life. He even claimed to have experienced a miracle. Abaddon told Locke that if he did the walkabout that when they met again, he would owe him one. ("Cabin Fever")
Abaddon had some hand in the creation of the four-man team that arrived on the Island. He was seen explaining to Naomi her mission to transport the other team members onto the Island, and to look after them. In spite of her objections, he explained that every member of her team was chosen for a specific reason. When Naomi asked what she should do if they were to encounter survivors from Oceanic 815, Abaddon reiterated ominously that there were no survivors and repeated her assignment, ensuring she was up for the task. ("Confirmed Dead")
After the rescue of the Oceanic Six
Abaddon visited Hurley at the Santa Rosa Mental Health Institute after Hurley had been re-incarcerated. He told Hurley that he was an attorney for Oceanic Airlines and offered to improve Hurley's living conditions by moving him to a nicer hospital. When Hurley became suspicious, Abaddon asked him, "Are they still alive?" Hurley became agitated and Abaddon abruptly left. ("The Beginning of the End")
Soon afterward, Abaddon was reunited with John Locke when, under the instruction of Charles Widmore, he became Locke's driver, taking him wherever he needed to go in order to persuade the Oceanic Six to return to the island. Abaddon kindly offered any assistance Locke required, including looking up anybody from his past. After unsuccessful trips to meet Sayid, Walt, and Hurley, Locke finally asked what he exactly did for Widmore. Abaddon replied that he gets people to where they need to be. After visiting Kate, Locke persuaded Abaddon to locate his ex-girlfriend, Helen Norwood.
Abaddon is gunned down by Ben
However, Abaddon discovered that Helen had died from a brain aneurysm, and took Locke to visit the graveyard where she was buried in Santa Monica. As they stood at her grave, Abaddon posited that Locke's fate, and his death, may be predestined. Locke argued that he didn't want to die, and if it was predestined then that would remove the choice. Abaddon, ending the conversation, simply remarked "Hey, I'm just your driver".
While preparing to leave the cemetery, Abaddon was suddenly shot by an unseen attacker, his blood showering the rear windshield of the car. Completely astounded, he took two more bullets to the torso before finally collapsing dead on the road. Benjamin Linus later told Locke that it was he who had shot Abaddon, who he claimed was "extremely dangerous" and would have tried to kill Locke in due time. ("The Life and Death of Jeremy Bentham")
- During chapter 1 of the Find 815 alternate reality game, a clue word for Season 4 was needed to progress. The game could be played on either ABC's website or Channel 7's website. The game revealed the clue word "Matthew" on ABC's website and "Abaddon" on Channel 7's site.
- A number of sources suggested based on casting information that this character was to be named "Arthur Stevens".  When asked about the subject, the producers said that fake names are used and fake scenes are read for characters to preserve secrecy.
We actually [have] the actors read fake [scenes] and give them fake character names because those casting [pages] travel so widely, there's no way to maintain secrecy. So we basically have to come up with fake but analogous scenes that will show us qualities of an actor but won't give away what the role is. So yes, the stuff out there is not totally accurate.
Source: Entertainment Weekly (Spoilers regarding casting also mentioned)
- The casting call described Arthur Stevens as "Appearing in 401 and 402, with possibly more eps down the line. He is a ruthless corporate recruiter, tall and thin, with a chilling presence." 
- "Abaddon" is the name of the biblical Angel of the Abyss (Revelation 9:11). The name is Greek for "destruction" or "the destroyer". As a place, it is likened to Sheol or hell.
- Many Biblical scholars believe Abaddon to be Satan or the antichrist. Others have stated that he may be one of the lesser demons of hell, or even a dark angel. 
- Abaddon/Appolyon/Apollo - The name is rendered in Greek as Apollyon and described as king of the locusts which rose at the sounding of the fifth trumpet. "In appearance the locusts were like horses arrayed for battle; on their heads were what looked like crowns of gold; their faces were like human faces, their hair like women's hair, and their teeth like lions' teeth; they had scales like iron breastplates, and the noise of their wings was like the noise of many chariots with horses rushing into battle. They have tails like scorpions, and stings, and their power of hurting men for five months lies in their tails. They have as king over them, the angel of the Abyss; his name in Hebrew is Abaddon, and in the Greek he has the name Apollyon." (Revelation 9:7-11)
- Abaddon is mentioned again elsewhere in revelation "And the fifth angel blew his trumpet, and I saw a star fallen from heaven to earth, and he was given the key of the shaft of the bottomless pit; he opened the shaft of the bottomless pit and from the shaft rose smoke like the smoke of a great furnace, and the sun and the air were darkened with the smoke from the shaft." (Revelation 9:1-2)
- Revelation 8 only has 13 verses. Revelation 9:2 is an alternate way of numbering Revelation 8:15 (815).
- Abaddon is pictured as a human sized locust, and is known as the lord of pestilence. "Then from the smoke came locusts on the earth, and they were given power like the power of scorpions of the earth; they were told not to harm the grass of the earth or any green growth or any tree, but only those of mankind who have not the seal of God upon their foreheads; they were allowed to torture them for five months, but not to kill them, and their torture was like the torture of a scorpion, when it stings a man. And in those days men will seek death and will not find it; they will long to die, and death will fly from them." (Revelation 9:3-6)
- In the press release for "The Beginning of the End" his name is misspelled with two "b"s and one "d"; in the press releases for "Confirmed Dead" it is spelled "Abaddon".
- The root for "Matthew" in Hebrew is "Gift from God." Additionally, in Hebrew, Abaddon is synonymous for Hell or destruction. VERY loosely translated "Matthew Abaddon" can be read as "Gift from the god of hell"*
- Jesus refers to God the Father as "Abba." "-don" is the first three letters of "donate," which comes from the Latin root for "give." The name of the character in the episode referred to by the press release using the spelling "Matthew Abbadon" might be interpreted "Gift of God/Father Gift."
- Abaddon is considered by some to be the patron demon of war
- This appears on the map - where the LOST island may be located - on the Mosaic Collective website part of the "Flash Forward" TV series ARG.
- Do not answer the questions here.
- Keep the questions open-ended and neutral: do not suggest an answer.
- For fan theories about these unanswered questions, see: Matthew Abaddon/Theories