The Eight Immortals are actual figures from Chinese legend (Taoism, specifically), being eight individuals who attained immortality and various other magical powers by various means, usually as rewards after being tested by a Taoist sage Lao Tzu or another immortal. The magical weapons and items used to banish the Demon Sorcerers in the second season are also associated with them.
In the Demon World Arc, Shendu wrote in the Book of Ages that all the eight Demon Sorcerers were never banished to the Netherworld, altering history causing the banishment never occurred. Curiously, their symbolic items were still capable of banishing the demons. This meant that they acted behind the scene to ensure the demons will still be banished regardless the historical alteration. This can be seen in the banishment chi spells were easier to perform such as the Immortal symbols conjured up a portal that pulled the demons inexorably back into the Netherworld, not to mention chi spell ingredients were no longer required.
Powers and Abilities
The Immortals were masters of good chi magic and formidable martial artists as well. In the flashback, all of them defeated the 8 Demon Sorcerers with very little effort. They also created the Pan'ku Box to seal the demons' portals. Furthermore, the common items that represent their symbols are capable of banishing the each of the Demon Sorcerers back to the Netherworld.
||Maiden in waiting||Flute||Hsi Wu|
|Crippled begger||Gourd||Bai Tza|
|Patron of actors||Castanets||Tchang Zu|
|Philosopher||Lotus pod||Tso Lan|
|Hermit alchemist||Drum||Po Kong|