All 4 Uses

immortal
in
Ready Player One
(Edited)

A lich was an undead creature, usually an incredibly powerful wizard or king who had employed dark magic to bind his intellect to his own reanimated corpse, thus achieving a perverted form of immortality.
p. 74.8

immortality = eternal life
In addition to being immortal and invincible, our avatars could go pretty much anywhere and do pretty much anything.
p. 313.7

immortal = not subject to death
"I'm entrusting the care of the OASIS to you now, Parzival," Halliday said. "Your avatar is immortal and all-powerful."
p. 363.8 *
His avatar is immortal and all-powerful.
p. 366.4

Definitions:

(1) (immortal)
living or existing forever

or:

someone famous throughout history

or:

someone who will never die -- such as a mythological god
(2) (meaning too rare to warrant focus)
More rarely, "The Immortals" denotes a military corps of the Persian Empire. The Immortals were so-named because each time a member of the 10,000 man corps was killed or seriously wounded, he was replaced by another man. They are best remembered in western culture for their role in defeating the badly out-numbered Spartans at the Battle of Thermopylae.