This class of Sacred Gears is specifically named after the Gehenna Atlas, the first and most powerful Sacred Gear to reach this rank, and like the Longinus, the Gehenna are utterly and completely unique, and only one of each may exist at a time. G.O.D. has stated that all Gehenna is just a combination of one ability with another. Essentially, they combine powerful abilities that aren’t supposed to be combined, and have the ability to end the world and kill even Gods, with ease.
Out of the nine, five have appeared in Jester of the Gremory Clan thus far, but G.O.D. has mentioned that similar to the Longinus, more Gehenna might be born, but they must become an Longinus first.
The Gehenna Atlas (ゲヘナアトラス, Gehena Atorasu), also known as the All Knowing Book of Books, the Incarnation of Anarchy, or the Atlas of the Cursed.It is the first and most powerful Gehenna, and was one of the three first made Longinus alongside the True Longinus and the Twin Triaina. It is currently wielded by Eri Beatrice, the descendent of the first and original, Wizard of Oz.
The Ginnungagap (ギンヌンガガプ, Gin'nungagapu), also known as the Society's Depiction of Isolation and Nature, is a high-tier Gehenna in the form of an scroll, that has the ability to isolate an person or entire country to an alternate dimension that even the Longinus, Aeon Balor and Telos Karma can destroy and the person can only escape if they find the randomly selected escape route, or if the possessor of the Gehenna dissipates the dimension, and lets free ever thing inside the dimension. It is currently wielded by Mare Alice Elaine.
The Nexus Chalice (ネクサスシャリス, Nekusasu Charisu), also known as the Secluded Head Grail of the Biblical Lovechild, is a high-tier Gehenna, and is an "Holy Grail" made from a fragment of the original Holy Chalice, and is seen as an more advanced version of the Sephiroth Graal. It has the ability to make contracts with the Principalities of Life and Death and heal wound such as limb loss, and also has the ability to completely cancel out the effects of other healing-type State-Change Sacred Gears such as Sephiroth Graal and Twilight Healing. It is currently wielded by Mae Elizabeth Westcott.
Billion Blades (ビリオオンブレード, Birion Burēdo), also known as the Unlimited Blade Works, is a Gehenna with the ability to create countless swords of Holy, Demon or Holy-Demonic nature, with various attributes and abilities such as elemental control, creature summoning and Dragon, Evil Beast and God Slaying capabilities. It is currently in possession of Shirou Muramasa.
Dawn Downfall (ドーンダウンフォール, Dōn Daunfōru), also known as the Magician of Insanity and Control, is an Gehenna that has yet to appear in the series. It is currently in possession of an unnamed Bishop of Jackson Nebiros' Peerage.
Yahweh's Hand (ヤハウェのハンド, Yahau~e no Hando), also known as the Young Angel Heroes with Eternal Halos, is an Gehenna that has yet to appear in the series. It is currently in possession of Heaven, alongside Armageddon Extinction.
Armageddon Extinction (ハルマゲドン絶滅, Harumagedon Ekusutenshon), also known as the Doll of Every Aspect of Destruction, is an Gehenna that has yet to appear in the series. It is currently in possession of Heaven, alongside Yahweh's Hand.
The name Gehenna is based upon an small valley in Jerusalem.
All of the high-tier Longinus have the potential to become Gehenna.
G.O.D. has stated that the six-strongest Longinus, even the True Longinus are comparably weak when compared to even one of the Gehenna, as only the six-strongest Longinus have the ability to destroy the world as all the Gehenna have that capability.