Dragon Handle

Meliodas' broken sword or the Dragon Handle was his primary weapon until it was stolen. Useless as a weapon by itself, Meliodas used the broken sword in conjunction with his ability Full Counter. It is later revealed that the handle originally was not a sword and was actually a fragment of the Coffin of Eternal Darkness.

Appearance
This sword has a broken blade attached to a green hilt. The hilt has two handles in the design of a twisted dragon which has three spikes on its head and on its back. The longer handle has the dragon's head at the end while the shorter handle has what appears to be a claw.

Background
The hilt of the sword is a fragment of the Coffin of Eternal Darkness, and, therefore, a key to the revival of the Demon Clan which was sealed away during the Holy War 3,000 years ago. This causes it to be part of a plot for the resurrection of the Demon Clan by Hendrickson, a Great Holy Knight of Liones.

History
Having acquired it through unknown means, Meliodas, according to Ban, had never let go of the broken sword since joining Seven Deadly Sins. Once, before the assassination of Zaratras, Ban, intrigued that the captain never let go of the weapon, questioned the captain about it. Not receiving a satisfactory response, Ban tried to steal it and was given a lasting wound by Meliodas, who used the broken sword as well as the enchantment Hellblaze,

Baste Dungeon arc
While in Dalmary Town, Meliodas, having been fatally poisoned by Dr. Dana earlier, suddenly regains consciousness when Golgius of the Weird Fangs tries to grab the sword from his hand. Releasing an aura powerful enough to scare the Holy Knight, Meliodas declares that he will not let go of the object even if he dies, and that this was the only way he can atone for his sins. His eyes are colored jet black, and his demon mark is present on on his forehead.

Capital of the Dead arc (manga only)
When Oslo blocks their way to the entrance of the Capital of the Dead, Meliodas, stopping Ban from killing Oslo, slightly unsheathes his sword, and creates an immensely huge ethereal dragon-like creature, which resembles the dragon on the sword's hilt, scaring the creature away. It also seems to be visible only to the Black Hound.

Vaizel Fight Festival arc
When Veronica causes Meliodas to be sealed in goddess amber during the attack by the Holy Knights in Vaizel, the sword falls to the ground. Elizabeth grabs it as well as the goddess amber and yells at Veronica to bring Meliodas back. Veronica signals Griamore to trap Elizabeth with his magic power, Wall, and he obliges. Ban grabs Veronica and threatens to hurt/kill her if Griamore does not release Elizabeth. However, Ban is attacked from behind by Jericho, and releases Veronica. Guila, who had arrived with Jericho, states that they have acheived their objectives and requests that Griamore release his magical ability. Elizabeth falls to the ground and Guila asks for her hand, but Veronica pushes Guila's hand away, stating that she will bring Elizabeth back to the kingdom herself and that Hendrickson's objectives are only that of Meliodas and the sword. Guila threatens Veronica to hand over Elizabeth, but is sealed with Jericho in Griamore's Wall. Elizabeth runs away with Veronica chasing behind her. Elizabeth steps on a mine planted by Guila, but Veronica sacrifices herself to push Elizabeth out of the way. Due to Veronica's fatal injury, Griamore's focus deteriorates and his magical ability is released. Guila attacks Griamore and picks up the broken sword which Elizabeth had dropped, asking the princess to cooperate. Elizabeth pleads Meliodas to help her and he breaks out of the goddess amber, with a black marks accross his body, as well as black eyes and a demonic presence. He takes the sword from Guila, her hand along with it. She expresses surprise and pain and Meliodas discards her hand. He waves the sword towards her causing a large blast. Meliodas flies to the location where Helbram and King were fighting and attacks. Meliodas is defeated by Helbram with the help of Hendrickson. The sword is stolen by Helbram while Meliodas is knocked out. Helbram detaches the damaged blade from its hilt, throwing the blade aside, and reveals that the hilt is a key to the revival of the Demon Clan.

Kingdom Infiltration arc
Helbram presents the dragon handle to Hendrickson, who places it in the center of the assembled Coffin of Eternal Darkness. This causes the Coffin of Eternal Darkness to be completely assembled except for the blood from an apostle of the goddesses.

Abilities
The hilt of the sword, the fragment of the Coffin of Eternal Darkness, displayed the ability to create an immensely huge ethereal dragon-like creature, that resembles the dragon on the other side of the hilt, and seems to be visible only to the victim. It was revealed that the Broken Sword has the power to open the gate to the Demon realm, but only a little.

Trivia

 * It was revealed that the Broken Sword isn't a sword but a key.