Immortals

The Immortals (不死者 fushisha) are a group of people who attained immortality, stopped aging and became impervious to injury.

All immortals must follow a set of rules and guidelines. Although they are able to use a false name for temporary introductions to mortals, their bodies reject all attempts to establish lasting false identities. In addition, they must use their real names when speaking to another immortal. Immortals can transmit information and images to another immortal by placing their left hand on the other's head and thinking about the information or image. To kill an immortal, another immortal must "devour" them by placing their right hand on the other's head and thinking "I want to eat you." In addition, the more often an immortal is injured in a certain way, the faster they will recover from that injury.

History
How many immortals their have been and for how long immortality has become possible is unknown. Thus far atleast three generations of immortals exist the first being the generation of Renee Paramedes Branvillier and Dalton Strauss who told Maiza Avaro how to summon the demon. Dalton had said that he and his ten students summoned the demon and attained immortality, but only three survived till now: him, Renee, and Archangelo (who devoured the rest). It is unknown if there are any other generations, so for the sake of convience and until this matter is put to rest they shall be classified as "Elder Immortals" until further clarifications come to light.

The second generation of immortals were a group of about thirty alchemists who were traveling aboard the ship Advenna Avis in 1711. Aboard the ship, they summoned a demon in the hopes of gaining immortality. They are successful and the demon gives them the Grand Panacea. Their leader Maiza Avaro is given the formula for the elixir. Later, the group decides they must keep immortality to themselves. Szilard Quates disagrees and devours thirteen of the alchemists, obtaining half of the formula Maiza gave to his brother, Gretto Avaro. Realizing the danger Szilard poses to them, they scatter throughout the world. Szilard devours five more of original immortals, bringing the total to eighteen, before he himself is devoured.

A third and most recent group of immortals is created in 1930 after Szilard manages to recreate the elixir, but loses possession of it. After it is passed around Manhattan by gangsters believing it is alcohol, Isaac Dian and Miria Harvent, the three Gandor brothers, Firo Prochainezo and all of the Martillo executives drink it at a party.

Those who drank Szilard's incomplete immortality elixir become partially immortal. Although they can be killed through devouring, they cannot devour back and do not stop aging. Huey's Homunculi in the Lamia are the "Other half"

Limits, qualities and potential
Being immortal means that they are completely impervious to death under many circumstances, excluding solely being "devoured" by another immortal. To devour an immortal, the eater must place his right hand atop of the head of the person he wishes to devour. Then he must think the words "I want to eat". The process of devouring seems to be painful given the horror-stricken expressions of death that most show when they are devoured (at least in the anime). The devourer then "inherits" all of his victim's memories, abilities, and knowledge. Devouring may not be limited to immortals, as Ronnie Suciart proclaimed himself capable of devouring despite being a demon (though given the details on demons at this point in the story leaves to question many things that are addressed later on). Though lethal, it is not impossible to survive an attempt at being eaten, as exemplified by Fermet on at least two occasions, despite the large gap on knowledge on how he survives, without the present devourer being aware of it, nor how Fermet's method was not later copied by the immortal who was eaten by Szilard. Surviving the devouring process also seems to corrupt the "inherited" memories, given Firo's inability to properly recall Fermet's memories, but it could also be the fact of the significant gap of inherited devourers (mainly being from an original immortal to Szilard to Firo making it no less than a three generation gap of sorts). Czeslaw Meyer also seems to be unable to recall certain aspects of Fermet and could only accurately remember Fermet's sadism in torturing him (though the justified trauma of constant torture for many years may have had an impact on what he can actually remember).

Devouring aside, Immortals are highly durable as they can recover from any injury in a matter of seconds ,and the more an immortal receives a certain type of injury, the quicker they heal from it, showing that despite immortals having stopped aging, they do not stop changing and adapting like mortals do. Though they will not die, an inflicted injury will still cause pain. Some of the injuries that immortals and partial-immortals have been seen recovering from include being shot, stabbed, beheaded, the breaking of their necks, and extremes such as being encased in cement and sent into the river to drown constantly and being pressed head-first onto the railway in front of a moving train. When the latter happened to Czeslaw Meyer, his blood and body tissues raced to him at constantly increasing speeds, eventually catching up to a speeding train. One of the best exemplified feats of endurance shown was by Denkuro, who was frozen for nearly three hundred years and yet survived thanks to his immortality. The only limitation is that should their body parts be taken away, then the immortal will not have the body part to attach to become reunited. Some body tissues, such as hair and nails, appear to grow and are capable of being cut naturally as Fermet has cut his hair.

However, immortality is an ability and not a tool. While immortality will provide basic advantages, one's own abilities need to be taken into account when facing certain opponents in combat. Berga coming out of his fight with Claire Stanfield was only due to his immortality, but he was still outmatched and unable to fight back, and Luck Gandor passed out after his long battle, proving that certain bodily functions are still prone to fail under circumstances against the body. Incapacitating the immortal and tying them up will also stop them from doing any harm, and during their time in the land of death, so to speak, they are vulnerable and defenseless to other attacks or strategies to incapacitate them.

Demons

 * Ronnie Sukiart (Advenna Avis' demon)

Homunculi

 * "The Poet"
 * Adele
 * Christopher Chareau de Red
 * Ennis
 * Hong Chimei
 * Leeza Laforet
 * Sham
 * Sickle
 * Reil

Grand Panacea

 * Elmer C. Albatross
 * Czeslaw Meyer
 * Denkuro
 * Begg Garotto
 * Fermet
 * Gretto Avaro
 * Huey Laforet
 * Maiza Avaro
 * Nile
 * Renee Paramedes Branvillier (before Advenna Avis)
 * Sylvie Lumiere
 * Szilard Quates
 * Victor Talbot
 * Zankuro
 * Nikki

Cure-All Elixir

 * Berga Gandor
 * Keith Gandor
 * Luck Gandor
 * Isaac and Miria
 * Senna
 * Mr. Yagu and several other members of Martillo Family, including Firo Prochainezo, Randy and Pecho

Incomplete immortals

 * Dallas Genoard and his cohorts