The Immortals are a group of [approximately] 500 people gifted/cursed with immortality. Although their origins are unclear, Brother Michael noted, upon discovering that Dr. Jordan was an immortal, that she couldn't have been because she "wasn't there." Although in season 1, Gunnar referred to himself as being a viking; whether this is true, or if he was rambling, is unknown. Also, the oldest immortal seen so far was Hatake, at over 500+ years old.
Immortals have the appearance of the general population ranging in ethnicity, gender, age and weight. The only traits that makes them distinguishable from humans is their silver eyes (hidden with either coloured contact lenses or dye being injected into the corneas), agelessness, and their faster healing rates and wound regeneration.
- Immortality - As their name implies the immortals are immortal and don't age, unless killed by violence. Multiple immortal deaths have been seen on-screen with various ways such as shooting, being bombed, and even decapitated.
- Immunity - As they are un-aging and immortal, they are either outright immune, or at least successfully resistant to most conventional diseases, ailments, and even 'mortally' lethal toxins. However, 30 years after the St. Germain outbreak, Mycosis is ravaging the mainland and killing off most of the Immortals.
- Accelerated Healing - Immortals generally heal faster than normal human beings. Also, they are usually capable of eventually recovering from many different types of wounds that would be fatal to normal humans (with Hatake healing fast after being burned in a snowmobile accident), provided they are largely 'intact' (Julia's left ring finger did not grow back, perhaps because it was not reattached in time).
- Their CSF (CerebroSpinal Fluid) is capable of curing cancer. Since Dr. Jordan was Immortalised herself, it is now known that their CSF is also capable of Immortalizing another mortal (provided the Immortal genetic material has not had time to transcribe specifically).
- It is believed that Julia Walker inherited the potential for immortality from her father, Hatake, and it was activated by her Narvik-B infection and Hatake's injection of his blood into Julia Walker. Sarah Jordan was Immortalized after receiving an infusion of Julia Walker's CerebroSpinal Fluid, which was only intended to cure her cancer.
- Someone can only be Immortalized if they receive CSF from a recently 'activated' immortal. After an unknown duration, the CSF will not work due to adaptive differentiation of the 'Immortal' stem cells, and will lead to disturbing physical deformities for the tardy recipient.
- Sarah Jordan, formerly mortal, was in her first trimester of pregnancy when she was Immortalized. The fetus remained in its first trimester developmentally for fifteen months until Sarah Jordan had her labor induced [against her will], with the immortal child being kept artificially alive.
- Although immune to most pathogens, they are susceptible to the St Germain Mycosis.
- Although Gunnar told Julia that she could survive without water for 4 days and food for 4 weeks, Brother Michael was kept imprisoned for 30 years without a way to obtain food and water, yet somehow survived, if somewhat frail.
- Immortality is found within a gene, however once the Immortal Genes are transcribed from DNA to RNA, they cannot be carried over. This is why Sarah Jordan became an Immortal upon receiving Julia Walker's Spinal Fluid (Julia had only been an Immortal for a couple days and her Immortal Stem Cells hadn't yet adapted to her body), while Landry suffered a seizure and became enlarged and grotesquely deformed upon receiving Sarah's spinal fluid (who had been Immortal for over a year). This could also be why so few Immortal children/offspring have been seen (Spencer Chissik, Julia Walker, and Sarah Jordan's Son), and why Brother Michael has yet to conceive an Immortal child by mating with his daughters for over 500 years.
- Immortals could be responsible for the myths about witches, or at least for the Salem Witch Trials, as a member of the Ilaria Board told Julia Walker, "she hadn't lived more than a lifetime, and watched loved ones burned at the stake."
Immortals have appeared in most, if not all episodes of season 1 and 2, however their true nature was not revealed until "Fushigi."
- Hiroshi Hatake
- Spencer Chissik
- Julia Walker (Immortalized by H. Hatake)
- Sarah Jordan (Immortalized by J. Walker)
- Sarah Jordan's Son
- Unnamed man Alan Farragut tortured for information
- 7 unnamed men on the board of Ilaria Corporation
- 2 unnamed women on the board of Ilaria Corporation
- Claire Wallenberg
- Alan Farragut (Immortalized, by whom is unknown)