The Great Dark Lords are the evil gods and goddesses who side in Tartarus (Equestria's form of Hell). They had an epic clash with the Great Lords with the Everlasting Dragons (Equstria’s version of the titans) at their side. Eventually the Great Dark Lords fell understand with the Everlasting Dragons deceased during the battle. They were sent to Tartarus for eternity. Like the Great Lords, The Great Dark Lords come in two groups: The Inner Circle, the main seven Great Dark Lords. And the outer circle, the minor great Dark Lords.

The Inner Circle:
Zalgo: (Belongs to creepypasta)

Zalgo is a malevolent and mysterious entity of chaos and evil that lives in a palace of tortured glass, served by legions of monsters forged from the tears of the undead, and each one clad in armor carved from the concentrated suffering of grieving mothers. He also is said to live within all mankind, waiting for the thin glass wall within them to crack, so that he may take over. His real name is Z'algatoth and he has a cult of followers who wish to bring about his coming. His hated rival is Mr. Creepypasta. http://ask-theangelofsouls.deviantart.com/art/Creepypasta-the-Fighters-Zalgo-440161560

Hexxus: (Belongs to Ferngully the last Rainforest)

Hexxus first appeared on Equestria in ancient times when the balance of nature shifted, at the time of the clash between the Great Lords and the Great Dark Lords . He rose out of the Earth and rained down poison, destroying much in his wake and killing countless living creatures, including humans. He was finally defeated by the by the Great Lords along with the other Great Dark lords and imprisoned Tartarus.
He is the god of destruction and pollution. His most hated Rival is Lauren Faust.
http://villains.wikia.com/wiki/Hexxus

Lucemon Chaos Mode: (Belongs to Digimon)

Lucemon Chaos Mode is a Demon Lord Digimon whose name and design are derived from the mythological Lucifer, the angelic name of Satan, with "Luce" (Ita: "Light"), "Chaos", and "Falldown" as a reference to that name. One of the "Seven Great Demon Lords", it represents the Sun and the sin of Pride. It is the strongest of the group, and possesses both the divine and the diabolic. It instigated a rebellion in the far-flung past, and so it was sealed in the Dark Area along with many other Demon Lord Digimon. Its power exceeds that of Megas, and is said to rival that of the existence called "God" as well. It has a contradictory existence, in that one side of it loves all things, as God does, while the other is trying to destroy the whole world, as the Devil does. Hence, once it destroys this world, it intends to create a fresh new world. http://digimon.wikia.com/wiki/Lucemon_Chaos_Mode#Lucemon_Chaos_Mode.
He is the second god of pride and corruption, and the brother of the six other Great Demon Lords. His enemies are the Ten Legendary Warriors, who are some of the champions who fought alongside the Great Lords. His six siblings are Laylamon, Leviamon, Belphemon, Beelzemon, Barbamon, and Daemon. Together they are known as The Seven Great Demon Lords , the digimon forms of the seven princes of hell.

Cthulhu: (Belongs to H.P. Lovecraft)

Cthulhu is described as "A monster of vaguely anthropoid outline, but with an octopus-like head whose face was a mass of feelers, a scaly, rubbery-looking body, prodigious claws on hind and fore feet, and long, narrow wings behind." Cthulhu has been described as a mix between a giant human, an octopus, and a dragon, and is depicted as being hundreds of meters tall, with human-looking arms and legs and a pair of rudimentary wings on its back. Cthulhu's head is depicted as similar to the entirety of a gigantic octopus, with an unknown number of tentacles surrounding its supposed mouth. http://en.m.wikipedia.org/wiki/Cthulhu.
The god of oceans, madness, corruption, reality, dreams, and the cosmos. He is one of the most feared.

Set: (Belongs to Tutenstein)

Set is known as the god of chaos, deserts, and plagues. He is the brother of Osiris, who is one of the Primordial Great Lords. He killed his brother, cut him into a million pieces, and tossed him into a river, but Isis,Osiris’s wife, revived him. Set was defeated by his Osiris who was added by the Great Lords, and sent to Tartarus with the other Great Dark Lords. Osiris has been Set’s hated rival ever since.

Eris:

Known as the goddess of chaos and wife of Set. She is the only female in the Inner Circle. Her most hated rival is Seath the Scaleless who was the one who betrayed her and her children the Everlasting Dragons. She is the mother of the Everlasting Dragons, the dragons being born from her dead skin.

Lucifer:

Lucifer was once God’s star pupil, until he tried to take over which caused him his downfall. He was sentenced to Tartarus with the other Great Dark Lords to spend eternity. He is the first god of pride, Lucemon Chaos Mode being the second. He has six other brothers being Asmodeus, Leviathan, Mammon, Belphegor, Beelzebub, and Satan. Together they are known as the Seven Princes of Hell. His most hated rival is his old master god.

Reminder: The links in this are things i don't own. No credit is taken except for things i own. I've added a few things in this thread as well as the other threads so the words i added are mine. And you can tell cause they don't have link urls. So the ones that have link Urls in this forum are things i do not own, and those that don't i do on. The pictur of Lucifer and Eris belongs to http://fc06.deviantart.net/fs51/f/2009/282/b/b/Lucifer_by_GENZOMAN.jpg and the pictures of Mammon, Asmodeus, Beelzebub, Satan, Belphegor,and Leviathan belong to http://darksilvania.deviantart.com. So enjoy.

The Outer Circle:

Leviamon: 9belongs to Digimon)

Leviamon is a Demon Lord Digimon whose name and design are derived from the mythological Leviathan. One of the "Seven Great Demon Lords", it represents Mercury and the sin of Envy. Called the "Devil Beast" out of terror of the exceedingly mighty power that it possesses, it is the strongest monster existing in the Digital World. This extensive monster, said to possess gigantic jaws which could guzzle down even the Digital World, is reported to sleep in the depths of the Net Ocean nearest to the Dark Area, and if it is awakened it will despise any Digimon at the top, and will run not away even from Angel Digimon, much less other Demon Lord Digimon. However, as the existence of the limits on Digimon are decoded, its own appears similar to nothingness, and it is said that it builds the foundation for the existence of wickedness in the Digital World. http://digimon.wikia.com/wiki/Leviamon
This creature is the second god of envy, Leviathan being the first. He was general of Chthulhu’s Lovecratean army. His endless jealousy can get the best of him, which is the reason of his defeat and descend to Tartarus along with the other Great Dark Lords.

Daemon: (Belongs to Digimon)

Daemon is a Demon Lord Digimon whose name is derived from the mythological Cacodaemon and whose design is derived from the mythological Satan. One of the "Seven Great Demon Lords", it represents Jupiter and the sin of Wrath. It leads the many Devil and Fallen Angel Digimon, and like Devimon it was originally an Angel Digimon, and a particularly high-ranking one. It is said that before it fell to the Dark Area and became a Demon Lord Digimon, it was in fact a Seraphimon. However, because it raged in fury or rebellion, against a being of goodness in the Digital World (perhaps the very human that created the Digital World), it was deleted to the Dark Area. It has vowed to one day conquer the Digital World, in revenge against the being of goodness. Also, while it led the rebellion, and was the strongest among the Megas, it plotted to secretly revive the "Super-Ultimate Digimon". The characters on its anklet read "010", four times. http://digimon.wikia.com/wiki/Daemon
Daemon is the second god god wrath, his counterpart Satan being the first. This Great Dark Lord is very short tempered and nobody wants to see his bad side. His anger got the best of him, which is the reason he descended to Tartarus with his brethren. His enemy is Gwyn, Lord of sunlight and Yggdrasil

Belphemon Rage Mode: (Belongs to Digimon)

Belphemon Sleep Mode

Belphemon Rage Mode is a Demon Lord Digimon whose name and design are derived from the mythological Belphegor. One of the "Seven Great Demon Lords", it represents Mars and the sin of Sloth. It is said that Belphemon Sleep Mode awakens from its eternal slumber once in a thousand years. When it awakens, it regains its natural shape and changes into an incarnation of rage, and anything that enters its field of vision becomes a target for destruction. It is said that just by suffering Belphemon Rage Mode's roar, Ultimate Digimon and below will have their data disintegrated and will instantly die, and not even Mega Digimon can escape unharmed. http://digimon.wikia.com/wiki/Belphemon_Rage_Mode#Belphemon_Rage_Mode
Belhphemon Rage Mode is the second god of sloth, Belphegor being the first. He can be lazy in his Sleep Mode, but once in his Rage Mode all hell is bound to break loose.
He was defeated easily due to his sloth and sentenced to Tartarus with the other Great Dark Lords. His enemies is Hanuman, Yggdrasil, and God.

Barbamon: (Belongs to Digimon)

Barbamon is a Demon Lord Digimon whose name and design are derived from the mythological Barbatos. One of the "Seven Great Demon Lords", it has the appearance of a bearded old-man and represents Saturn and the sin of Greed. It resides within the heart of the Dark Area, the den of demons, and manipulates Fallen Angel Digimon to run the whole gamut of evil. It is obsessed with all of the treasure which exists within the Network, so out of avarice, and regardless of the means, it has a cruel personality with a greed that would kill Digimon just for a piece of treasure. It is the foremost and most cunning schemer of the Seven Great Demon Lords, and can easily manipulate the Mega-level Ghoulmon in addition to Fallen Angel Digimon. http://digimon.wikia.com/wiki/Barbamon
Barbamon is the second god of greed, Mammon is the first. He was Lucifer’s trusted commander of the Fallen Angels and Lucemon’s high priest. He was defeated by the Jesus and Mary of Nazareth, his hated rivals, despite is army being outnumbered by Angels. And he was sent to Tartarus where he lives in a Golden castle with gems, jewelry, money, and other trinkets that he has pillaged.

Beelzemon: (Belongs to Digimon)

Beelzemon is a Demon Lord Digimon whose name and design are derived from the mythological Beelzebub. It is referred to as Beelzebumon L in materials where it appears alongside Beelzemon (2010 anime). One of the "Seven Great Demon Lords", it represents Venus and the sin of Gluttony. While it possesses the power to preside over the many Devil Digimon, it dares to observe a solitary existence. It is said that it could stand at the peak of the dark army, "Nightmare Soldiers", if it cared to, although it is also said that there exists a Demon Lord Digimon which surpasses even Beelzemon. It rides on the gigantic motorcycle-type machine, "Behemoth", holding its cherished shotguns, the "Berenjena" (Esp: Eggplant). Although its personality is cruel and merciless, it is also exceedingly prideful, so it would never attack the weak. http://digimon.wikia.com/wiki/Beelzemon
Beelzemon is the second god of Gluttony, Beelzebub being the first. His appetite is insatiable, like his counterpart Beelzebub. He is also the sharp shooter of the Seven Great Demon Lords. He was commander of Beelzebub’s insectile forces and was good at what he did. He was defeated by the hands Gywndolin with his Darkmoon Blade Covenant, and was exiled to Tartarus with his demonic kin.

Laylamon: (Belongs to Digimon)

Laylamon is a Demon Lord Digimon whose names and design are derived from the mythological Lilith. One of the "Seven Great Demon Lords", it has the appearance of a woman and represents the Moon and the sin of Lust. It is thought that it was originally an Ophanimon, but it fell from heaven and eventually became known as the "Goddess of Darkness". It confounds its opponents with its bewitchingly lovely appearance, and it is said that those who are taken in by its temptations are invariably granted death. Its reputation as the "Goddess of Darkness" is appropriate, as it offers generosity towards vice, but only cruel outrages towards virtue. The demonic "Nazar Nail" on its right arm corrodes everything it touches. http://digimon.wikia.com/wiki/Laylamon
She is the goddess of Lust and darkness, while her counterpart Asmodeus being the god of lust. She is one of Asmodeus’s wives as he’s known to have a harem.
When she was still an Ophanimon, she fell in love with Jesus. But was rejected due to him sensing an insatiable desire within her. This led her heartbroken and joined the Great Dark Lords. She was eventually defeated and sentenced to Tartarus with the rest of her demon kin. Her nemesis is Jesus to not only did he sent her to Tartarus to rot for eternity, but also broke her heart when he rejected her.

Mammon:

The second prince of Hell, Mammon, the Avarice's Wolf
His sole name is used to describe greed, avarice, and unjust worldly gain. A false god of excessive materialism, lust for wealth and unholy richness. He is the god of Greed. http://darksilvania.deviantart.com/art/7-princes-of-Hell-Mammon-212453604

Asmodeus:

The third prince of hell, Asmodeus, The Corruptor of desire.
Said to been born from the profane intercourse of mortals and demons, he is the demon of Lust and Lascivity. He tempts men and women with pleasures of the flesh, in order to separate them from their souls. http://darksilvania.deviantart.com/art/7-Princes-of-Hell-Asmodeus-213278402

Satan:

The fourth prince of hell, Satan, the Accuser
The original snake, the dragon of apocalypse, Satan is rage and anger at their purest form. Bringer of self-destruction, violence and hatred, he expelled men from Eden, and brought war and destruction upon the land of mortals. http://darksilvania.deviantart.com/art/7-Princes-of-Hell-Satan-214593556

Beelzebub:

The fifth prince of hell, Beelzebub, Lord of the flies
Like a plague of locust or an army of ants, Beelzebub is always moving, always eating. He only exists to plunder and devour, gulping and guzzling anything the crosses his path of ravaging consumption, being crops, cattle, flesh, bone, blood or soul. http://darksilvania.deviantart.com/art/7-Princes-of-Hell-Beelzebub-216093342

Leviathan:

The Sixth prince of Hell, Leviathan, the coiled one.
Imprisoned by God itself, his desire to be as great as angels and demons lead him to scape from time to time to eat the moon. But yet, desiring more, he became a prince and his mouth became the gates of hell itself. But yet, he wants more... http://darksilvania.deviantart.com/art/7-Princes-of-Hell-Leviathan-217416926

Belphegor:

Seventh prince of hell, Belphegor, the inventor.
The prince of sloth, Belphegor tricks men with inventions that will make their lives much easier, and will take them away from their hard jobs. But this is just a trap, in order for mankind to abandon activity, relaying them on machines, and thus abandoning their bodies, and minds and souls to sloth.

Dagon: (Belongs to H.P. Lovecraft)

Dagon is depicted as a gigantic Deep One (around 30 stories tall) and first appeared in the short story "Dagon" - since then he and his consort have more or less been established as the official rulers of the Deep Ones, though Mother Hydra seems to gain a slightly larger following. http://lovecraft.wikia.com/wiki/Dagon

The co-founder of the Loecraftean Army alongside Cthulhu. He is known as the Deep One and lurked in the deepest depths of Equestria’s oceans. He fought well at the clash between the Great Lords and the Great Dark Lords.
He was defeated by Susanoo easily and was sent to Tartarus where he claims the murky oceans of Tartarus as his domain.

He ha a deep grudge towards Susanoo, his grudge is as deep as the watery domain in Tartarus.

Terridax: (Belongs to Lego and Bionicle)

Over 100,000 years ago just before in Equestria, Teridax and the other Makuta were created by the Great Lords, using the substance known as the Antidermis. Later when the Brotherhood of Makuta was first formed by Miserix, Teridax was appointed as the lieutenant of the army of the brotherhood. http://villains.wikia.com/wiki/Teridax
Terridax betrayed Mata Nui and was involved in the clash between the Great Lords and the Great Dark Lords. He was eventually defeated by Mata Nui and sentenced to exile in Tartarus with the other villainous being. Since then, Mata Nui became his most hated nemesis.