Coffin of Eternal Darkness

The Coffin of Eternal Darkness is a powerful magical seal that had sealed away the dreaded Demon Clan for three thousand years until the present day in the series.

Appearance
The Coffin of Eternal Darkness takes an appearance of a circular disk that contains four fragments representing the Four Clans with the Dragon Handle at its center.

Background
Three thousand years ago, when the Four Clans emerged victorious over the Demon Clan, they created the Coffin of Eternal Darkness to seal them away and cut off their realm to the physical world, bringing the land of Britannia to an era of peace ruled by humans whilst the Goddesses, Giants and Fairies withdrew back to their respective realms. The Coffin was then broke off into fragments in hopes that the Demon Clan remained sealed. However few Demons namely the Red Demon, the Gray Demon and Fraudrin managed to escape the seal and went off separate ways either wreaking havoc in Britannia or plotting the revival of their Clan.

At some point, Meliodas received the Dragon Handle, the key to the Coffin and was tasked in guarding it at all costs with his life until ten years later when he lost it to Helbram in their chaotic battle in Byzel. Upon the completion of the gathering of fragments of the Coffin of Eternal Darkness with the addition of the newly-claimed Dragon Handle, the Coffin was complete although it only managed to barely open the rift of the Demon Realm for the demonic entities to get through to which Hendriksen concludes that Elizabeth Liones was needed for the completion of the ritual.

Despite his defeat at the hands of Meliodas, Hendriksen fled to Zhuhur Valley with the Coffin of Eternal Darkness. Nearly dying, Fraudrin appears as Dreyfus and heals him that allows the former Great Holy Knight to finally complete the ritual with the bandage cloth containing Elizabeth's blood, although it was complete, the ritual succeeded and nine Demons were released from the Coffin.

Abilities
The Coffin of Eternal Darkness is a very powerful seal formed by the magics of the Four Clans that it has kept the Demon Clan from entering the physical realm for three thousand years although it's not as perfect as few Demons managed to escape the seal. It also has a booby trap that kills anyone attempting to tamper the Coffin.

In order to break the seal, the Coffin requires all its fragments gathered with the Dragon Handle and the blood of the Apostle of the Goddess as the key to the release of the Demon Clan with a ritual that requires an incantation of an ancient language of Britannia.