As their name implies, at a certain point Immortals stop outwardly aging, generally at about twenty-five years, though apparently among East Asians possibly a little later.

Immortals receive no permanent scars and also never contract contagious illnesses, even during times of plague.

They remain fertile for as long as they live and can rapidly heal broken bones or other serious wounds.

Speculation on "recurrent intactness" among women is left unanswered, with the possibility of the female hymen likewise restoring itself having been brought up at one point during dialogue in the novel.

Immortals can and in the course of the novel do die, as they are not capable of recovering from injuries such as a stab to the heart or decapitation.