Ten Commandments

The are an extremely powerful group of ten elite warriors who are the strongest amongst the Demon Clan. Handpicked by the Demon King himself, each member possesses a, a unique power gifted to them by the Demon King, which delivers a unique curse to whomever breaks a rule specific to each member. This power is absolute; it cannot be opposed even by its wielder, although members of the Ten Commandments are immune to all other Commandments except for their own. The curses will only be lifted if the victim defeats its wielder or at the victim's death. The Commandments can be removed from their wielder if he gives his consent or if he is left powerless, unable to fight or die.

Overview
The Ten Commandments were formed when the Demon King had put the Demon Realm under his control, planned to give half of his power to his servants and thus conquer all at once. However, in order not to give too much power to a single individual and put his position at risk, he divided half of his power into ten fragments and handed them to ten of his elite warriors in the form of Commandments.

Three thousand years ago, the Ten Commandments fought for their race against the other four races (goddesses, giants, fairies, and humans) in the great, ancient Holy War. The Ten Commandments at that time were led by Meliodas until he ended up betraying them, killing two of its members, Aranak and Zeno, in the process that would later be replaced by Drole and Gloxinia. Another of its members, Gowther, left its position in the group when escaping from his prison in the Demons Realm and finally died, being his place occupied by Fraudrin. The group were finally defeated and sealed by the Coffin of Eternal Darkness alongside the rest of the Demon Clan. At some point, Fraudrin was somehow able to escape and began searching for ways to release his people, until the present day, where he manipulated Hendrickson into freeing the other nine members from the seal (as he did not have enough of Elizabeth's blood to break the seal completely).

As they were completely drained of their magical powers by an after effect of the seal, the Ten Commandments elected to head towards Edinburgh while leaving a terrified Hendrickson behind. Arriving at their destination, they were surprised to find a a castle in ruins, and a giant hole bored into the land. Zeldris deduces that the hole was made by Meliodas, but they had no way of knowing the castle was destroyed by Escanor.

Their presences in Britannia awoke two of the Demon Clan's Albion, one at Camelot and the other at the Fairy King's Forest, which were destroyed by Meliodas and King. Sensing the Albions' destruction, Galand was delighted to know that there are still powerful people even in the current age and decided to take action despite them still having yet to recover their full power. He traveled all the way to Camelot in 72 high jumps and encountered three members of the Seven Deadly Sins. He easily overwhelmed them and annihilated almost half a portion of Camelot and its citizens and slaughtered its Holy Knights in battle. However, Gowther's power Invasion deluded Galan about having killed Meliodas, Diane, Slader, and Merlin.

Later on, the Commandments continued to rest and recover their magical power through eating the souls of humans they devoured and were shocked when they sensed Meliodas regain his full demonic powers at Istar.

Suddenly, Meliodas appeared out of nowhere through Merlin's teleportation and casually greeted the Ten Commandments who were surprised by his sudden appearance. Zeldris and Fraudrin were going to attack him but Galand told all of them to stay out of it as Meliodas is his prey to kill. Melodias battled and defeated Galand in less than ten seconds before warning Zeldris that the Seven Deadly Sins will defeat the Ten Commandments with everything they've got, warning them of their doom if they stepped out of line.

In response, Zeldris and Fraudrin attempted to attack Meliodas from both sides, but he was teleported back to Istar. Galand was angered and humiliated by his defeat at the hands of the "Accursed Demon".

As Galand complains and demands that Melascula find Meliodas he is cut off by Zeldris as he tells him and the other demons that their goal is the domination of Britannia and commands the others to move out in groups of two (or more) in order to recover their magic power as quickly as possible and to use whatever methods they deem necessary to eradicate the other four races. Fraudrin then asks if this was a declaration of war against Meliodas which he replies saying that this isn't war but an extermination.

Still angered by his defeat and the thought of Meliodas being "beyond" him, Galand tries to claim to have been able to defeat Meliodas any time he wanted, however before he can finish his sentence he is stopped and warned about lying by Dolor, questioning if he had forgotten that the Ten Commandments would incur their own curses on themselves if they break their own laws. Galand then lowers his head in response but still curses Meliodas in his mind. The Ten Commandments then disperse, Zeldris and Estarossa, however, remain behind.

Derieri and Monspeet arrive at the town of Bellford where they promptly eat many people's souls. Drole and Gloxinia arrive at Vaizel at the construction site of a new "brawl colosseum", because Gloxinia finds the site and activities surrounding it interesting. Meanwhile Fraudrin arrives at the town of Ferson, where he is promptly attacked and seemingly defeated by members of the Pleiades of the Azure Sky, and then taken to the a research tower in Zeldon, while Gray Lord watches. Meanwhile, Merascylla, who teamed up with Galand, begins to resurrect the dead all over Britannia in order to wipe out the living people.

Upon noticing that one of her zombies is resisting her magic, Galand and Melascula arrive to see what is happening, from there a great battle ensues between them and Fox's Sin of Greed Ban and eventually Lion's Sin of Pride Escanor which ultimately results in their defeat and possible deaths. Dolor notices this, as well as what happened to Fraudrin, and relays this to his partner, as they patiently wait for all the unsuspecting prey to arrive at the "Fight Festival" they are holding to draw strong souls to them as a more efficient way of recovering their lost magic power.

Meanwhile, Fraudrin is being held captive by the Pleiades who intend to prove that humanity can best the ancient demons and even defeat a member of the legendary Ten Commandments. Fraudrin then reveals that he is not an actual member of the Ten Commandments, but a replacement for the missing member, Gowther. Grayroad then appears, disguised as Dogedo to retrieve Fraudrin. Denzel Liones, the leader of the Pleiades, lets them leave being cautious of Gray Lord's commandment. Fraudrin and Gray Lord then walk out, with Fraudrin stabbing Deldry in the gut as revenge for their last battle. Before going, however, Fraudrin questions why he is leaving them alive, blaming his time in a human as making him soft, and decides to kill them all and destroys their base. As it crumbles, Fraudrin and Gray Lord leave, ready to continue their mission. They are later seen resting in a cave.

Dolor and Gloxinia decide to organize a Great Fight Festival as an efficient way to gather strong souls together. Meanwhile, Derieri and Monspeet have completely wiped out the populations of nine cities and towns in northern Britannia. Estarossa and Zeldris apparently parted ways at some points, as Zeldris went on to conquer Camelot's royal capital single-handedly.

Drole and Gloxinia's festival is short-lived, as they are unexpectedly attacked by a participant whose power suddenly spiked tremendously. Afterwards, Meliodas attacks them both, and despite their best efforts, it seems he is going to kill them. But, before he can finish them off, all of the other Commandments (except Galand) arrive to aid them. After a grueling battle, in which Melascula is incapacitated unexpectedly by Ban, Estarossa seemingly kills Meliodas, and the eight remaining Commandments set out to solidify their conquest of Britannia.

A month after Meliodas' defeat, the Ten Commandments have Britannia under their thumb. They send out squads of lesser demons to terrorize people and stamp out any resistance and it has become common practice to sacrifice Holy Knights and other with strong souls as a form of appeasement. Some people do this to protect themselves and their families while others do it out of genuine adoration of the Ten Commandments.

Eventually, they set their sights on conquering Liones, however, one after another they are defeated by members of the Seven Deadly Sins. Estarossa and Zeldris are sent flying by Escanor, and later Fraudrin is dealt by a revived Meliodas, who definitively kills Fraudrin. Grayroad in turn is captured by Merlin. Drole and Gloxinia are no where to be found during this great battle, attending to other matters and finally deciding to abandon the Commandments and return with their respective clans. Melascula is finally defeated by all the Sins and stripped of her powers, being also captured by Merlin.

The only members still active are Estarossa and Zeldris, as Derieri and Monspeet decided to not heed Zeldris' calling to gather the Commandments and live in peace after being defeated by Meliodas.

Later, when Meliodas decides to become the new Demon King to break Elizabeth's curse, he affirms that to achieve this he must acquire the same power as the Demon King, which he can achieve by absorbing all ten Commandaments in himself. Already disposing Grayroad's Commandment, Melidoas allied with Estarossa and Zeldris, who already possessed the Commandments of Gowther, Drole and Gloxinia and instructed them to recover the other Commandments

Abilities & Power Levels

 * Derieri the Purity: Combo Star (52,000)
 * Estarossa the Love: Full Counter (60,000)
 * Fraudrin the Selflessness: Full Size (31,000)
 * Galand the Truth: Critical Over (27,000)
 * Grayroad the Pacifism: Curse (39,000)
 * Melascula the Faith: Hell Gate (34,000)
 * Monspeet the Reticence: Trick Star (53,000)
 * Zeldris the Piety: God (61,000)

Former

 * Aranak: Unknown
 * Calmadios the Piety: Unknown
 * Drole the Patience: Ground (54,000)
 * Gloxinia the Repose: Disaster (50,000)
 * Gowther the Selflessness: Invasion (Unknown)
 * Meliodas: Full Counter (60,000+)
 * Zeno: Unknown

Trivia

 * The "Commandments" from which the group's name is derived, all seem to be loosely based on one of the real Ten Commandments from the Abrahamic religions.