Fenric

Fenric, also known as Hastur the Unspeakable, Aboo-Fenrán, the Wolf and the Hunger, was an immensely powerful sentient force that was at least as old as the universe itself and an intelligence of pure evil, later identified as a Great Old One.

Nature and powers
Fenric did have a body, one with a thousand limbs that stretched across several dimensions, (AUDIO: Gods and Monsters) but like many Old Ones lost it and became dependent on possessing others. He could presumably inhabit any body in any time, possibly killing the original consciousness if suppressed long enough. (AUDIO: Black and White) If a body became too weak, he would transfer into another. He was able to teleport and could cause lightning strikes. While imprisoned, he was still aware of events outside the Shadow Dimensions and could move people through time and space in time storms, whilst also influencing their destinies without them knowing. These individuals, who had been touched by the curse of Fenric, were known as the Wolves of Fenric. (TV: The Curse of Fenric) He was able to control an army of Haemovores, though this was a drain on his mind, and he was able to bestow free will onto individual creatures. (AUDIO: Gods and Monsters)

Relationship with other Old Ones
Fenric was seen as being too dangerous, even for the Elder Gods who were capable of dying despite their great power. As Weyland's shield gave the wearer the ability to destroy matter and change reality, Fenric sought it while the other Gods supported Weyland in his game against Fenric, with the shield as the prize. He was infuriated when he learned of the conspiracy against him. (AUDIO: Gods and Monsters)

Origins
The being later known as Fenric was one of two forces, one good, one evil, which were present at the Dawn of Time and became caught in it. Somehow, the evil force survived. (TV: The Curse of Fenric)

Some sources state that Fenric originated not in the beginnings of this universe but, like the other Old Ones, in a universe before this one. These accounts state that Fenric bore the name of Hastur the Unspeakable. (PROSE: All-Consuming Fire) The name Fenric came from a mythic figure in Norse mythology. The myths described a monstrous wolf which would, during the final battle between gods and beasts, destroy the world at the end of time. (TV: The Curse of Fenric)

Entrapment of Fenric
Prior to his sixth regeneration, (PROSE: The Quantum Archangel) the Doctor's first known encounter with Fenric was in Constantinople in the middle of the 3rd century. Fenric (then known as Aboo-Fenrán) had been terrorising the area, when the prince El-Amjad tried to force him to leave. Fenric agreed, provided the prince gave him the first thing he named when he returned to his castle. El-Amjad agreed to this, but when the first thing El-Amjad named was his youngest daughter (due to the meddling of Fenric), he instead sent a chest of gold. When Fenric learned that El-Amjad would not give up his daughter, he continued to ravage the countryside.

Eventually, the Doctor arrived in the city, and agreed to help in exchange for freeing a slave called Zeleekhà. The Doctor went out to Fenric and challenged him to a game of chess, (PROSE: The Curse of Fenric) with Fenric carving pieces from the bones in the desert to play against the "lonely old man". (PROSE: The Runes of Fenric) After forty days of stalemates, the Doctor was able to convince Fenric that with one move, he would win. Fenric spent another 40 days trying to figure out what this one move was, growing weaker all the time. Eventually, he became so weak that the Doctor was able to trap Fenric in a flask and banish him to the Shadow Dimensions. (PROSE: The Curse of Fenric)

Imprisonment
At some stage of Fenric's imprisonment, he briefly met and played a game of chess with the Celestial Toymaker. The Toymaker wished to claim Fenric as his new toy, while Fenric wished to take possession of the Toymaker's body so he could escape his prison. However, the game ended in a stalemate, and the Toymaker departed, leaving Fenric trapped. (PROSE: Games)

Fenric's stratagem
Fenric's power was such that his influence still continued to pervade space and time. He set into motion events that would ensure his escape. (TV: The Curse of Fenric)

Fenric summoned the Ancient One, the last Haemovore, from the future. When Vikings stole the flask containing Fenric sometime after the 10th century, the Haemovore followed them and the flask to Northumbria and Maiden's Point. On the flask's voyage, in the North Atlantic Ocean, the Vikings encountered a crashed Ice Warrior vessel holding a parasite the Martians called "The Flood". Fenric planned to use it to infect the Earth's water and release him, but was stopped when the Twelfth Doctor told an older Haemovore, the Haemovore Prime, of this betrayal. This caused his former puppet to detonate a volcano and wipe-out the virus' strain. (COMIC: The Wolves of Winter)

Now knowing of and fearing its evil influence, the remaining Vikings buried the flask beneath St. Jude's Church, leaving a runic inscription warning that the flask was cursed. The remaining Haemovore remained beneath the waters of Maiden's Bay, gradually recruiting new members. The Haemovores, also known as the Wolves of Fenric, awaited their master's release. (TV: The Curse of Fenric)

Manipulating the timelines, Fenric ensured that the Sixth Doctor regenerated into a "baffled innocent". Despite the Seventh Doctor starting out as a "hapless imbecile", he still managed to triumph over Fenric's manipulations on Paradise Towers and Tollport-G715. (PROSE: The Runes of Fenric) He also transported Ace to Iceworld by time storm so that she could meet the Doctor and join him on his travels, (TV: Dragonfire) after ensuring she had "darkness" in her past. (PROSE: The Runes of Fenric) As Ace bore the "curse", Fenric hoped that he could use Ace as a weapon against the Doctor. (TV: The Curse of Fenric) Fenric then maneuvered the pair to the Psychic Circus, (PROSE: The Runes of Fenric) and, as she conducted a black magic ritual, used a time storm to whisk Lady Peinforte from her native time period of 1638 to 1988 to retrieve the Nemesis statue. (TV: Silver Nemesis)

Escape and defeat
In 1943, Maiden's Point served as a the location of a military base housing the ULTIMA, an early computer designed to decypher German code. The ULTIMA also had the secret purpose of translating the runic descriptions and so freeing Fenric. Once released, he occupied the body of Doctor Judson and had the Haemovores, already killing every human they could find, summon the Ancient One from his dormant state. Fenric later possessed Soviet Captain Sorin.

The Doctor attempted to trap Fenric once again using a game of chess, as before, but having taken over Sorin's body, Fenric had learned the solution to the chess puzzle. Fenric was finally defeated when the Ancient One turned on him, destroying Sorin's body and leaving Fenric without a corporeal host. (TV: The Curse of Fenric)

Triumphant return
Fenric was returned to the "outer darkness" for a couple of years when he began playing a game against another Elder God called Weyland for control of Weyland's shield, an artefact which could grant omnipotence to an Elder God. As a response to this, Weyland had started to use the Doctor, Ace and Hex as pawns to track down and deliver him the shield. When Fenric became aware of this, he began tailing the TARDIS crew unbeknownst to them. (AUDIO: Gods and Monsters) However, Fenric had unintentionally made his presence known to the Doctor when he left a chess set in a Swiss sanatorium where the Doctor was battling the Celestial Toymaker. (AUDIO: The Magic Mousetrap)

After this discovery, the Doctor began battling the Elder Gods more frequently, in an attempt to draw more attention from them, so he could eventually discover the conspiracy that he had become involved in. He fought the Karnas'koi with Ace and Hex in Alaska, (AUDIO: Lurkers at Sunlight's Edge) and he then began travelling in a Black TARDIS with Sally Morgan and Lysandra Aristedes, who helped him fight the Mi'en Kalarash, (AUDIO: House of Blue Fire) Derleth (AUDIO: Project Nirvana) and Moloch. (AUDIO: Protect and Survive) When his activities had drawn the attention of Fenric, he stranded the Doctor in 5th century, Denmark. There, he temporarily inhabited the body of a local Norse warrior travelling with Beowulf, and transported the Doctor to another dimension. However, what Fenric didn't anticipate was the Doctor providing his companions with the necessary information to rescue him, and giving them Weyland's shield. (AUDIO: Black and White)

The shield guided the TARDIS crew to the pocket dimension that the Doctor had been transported to, and there they discovered that they had been pawns used by Weyland to further his masterplan. Fenric had taken the body of a Scandinavian warrior living in the 9th century, and discovered that Weyland constructed his shield at the behest of the other Elder Gods, who saw Fenric as an uncontrollable element, and attempted to manipulate him to his destruction by leading him on a quest for Weyland's shield, an artefact that would inevitably destroy him. Weyland then tried to get his pawn, Hex, to use the shield to destroy Fenric, but his plan backfired when Hex regained control and used the shield on Weyland. After the game was finished, the pocket dimension began to collapse and Fenric possessed Hex. Hex sacrificed himself to prevent Fenric from permanently taking control and gaining power, saving the Doctor, Ace, Sally and Lysandra. When Fenric's corporeal form was destroyed by the collapsing dimension, he was left as a disembodied entity, alongside Weyland and Hex. (AUDIO: Gods and Monsters)

Legacy
Fenric was a part of one Gallifreyan prediction of the final apocolypse, where the Timewyrm would devour Rassilon when Fenric slipped its chains. (PROSE: Timewyrm: Revelation) On personal terms, their encounter with Fenric left an impression on the Doctor and Ace who would continue to think about it in their travels, Ace particularly remembering her experience in the time storm. (PROSE: Cat's Cradle: Witch Mark, Nightshade, Love and War)

Behind the scenes

 * Characters called the Gods of Ragnarok had appeared in The Greatest Show in the Galaxy, a story from the previous season of Doctor Who. Because they did not wish to confuse the public by having the same name appear in two different contexts, the production team forbade Ian Briggs, the writer of The Curse of Fenric, from using the name, to describe the apocalyptic time prophesied by Norse mythology when would break free of his chains and eat , the father of the gods. The writer also used the name Fenric for the great wolf, rather than the usual name. Hastur is the name of an Old One in the Lovecraft mythos.
 * Fenric is mentioned in a deleted scene from The Infinite Quest, as one of the beings which ruled the universe during the Dark Times.
 * According to the reference book The Doctor: His Lives and Times, Fenric was responsible for the Doctor's regeneration from his sixth incarnation into his seventh. He was also responsible for many of the Seventh Doctor's adventures prior to his arrival at Maiden's Point. He told Lady Peinforte who the Doctor really was by "whispering words in her ear".
 * The name “Hastur the Unspeakable“ comes from Ambrose Bierce’s story “Haïta the Shepherd“ but was popularised by Robert W. Chamber’s “King in Yellow” and H.P Lovecraft's “The Whisperer in Darkness”.