Scylla Io

Scylla Io (スキュラのイオ, Sukyura no Io) is one of Poseidon's Seven Marina Generals, and he guards the South Pacific Ocean.

Scylla, The Terrible Beast Of The Deep
Scylla Io first appears in vol.16 of the manga and in the episode 102 of the anime. His duty was to guard the Mammoth Pillar of the South Pacific Ocean, which supported Poseidon's Undersea Temple.

Andromeda Shun was on his way to the Mammoth Pillar of the South Pacific Ocean, and upon reaching it, he felt the chains of the Andromeda Cloth warning him of danger. Before him appeared a young maiden who seemed to pose no threat, but the chains were enraged and tried to attack. After Shun stopped them, the young maiden transformed into a horrible sea monster with a body comprised of a woman, a wolf, a bear, a bat, a giant bee, an eagle and snake.

It was an illusion created by Scylla Io, one of Poseidon's Marina Generals, who wouldn't hesitate to kill any intruder, specially if he or she posed a threat to his master. At first and as always, Shun tried to solve the situation with words, but he was forced to fight, because Io wouldn't stand idle while a Saint of Athena was trying to demolish the Mammoth Pillar he was responsible for keeping guard off. At first, Shun was overpowered by Io, who living up to the reputation of the beasts he represented, was a terrible enemy. Io used his many techniques, each of which represented a part of Scylla, to mercilessly attack Shun, leaving him close to death. Shun seemed to have no hope against the huge array of techniques Io possessed.

Shun, not willing to give up even half-dead, found the strength he needed to go on. Io decided to kill Shun at once and attacked performing his lethal moves, one by one. But Io was surprised to know that Shun had also found a way to counter each one of them. The mighty Andromeda chains would take a defensive method against each move Io had, depending on which one he performed. For the Eagle Clutch and Queen Bee Stinger, it would change shape to a net, for the Serpent Strangle, it would be the chain that would strangle the serpent, for the Vampire Inhale, the chain would strike each one of the attacking bats, for the Wolf's Fang, the chain would counter it taking the shape of a wolf trap, and for the Grizzly Slap, the chains would trap Io and render him motionless, shattering his Scale. Having defeated each one of Io's attacks and seemingly destroyed any tangible means of him attacking, Shun promised Io to set him free once he had demolished the Mammoth Pillar. Enraged, Io managed to break free from Shun's chains, and used his final trump card; Big Tornado. The attack overwhelmed Shun, striking him down repeatedly, making his Cosmo ablaze to the extreme and making him achieve the Seventh Sense. Shun engaged Io in battle again, and managed to deflect his Big Tornado attack and chain him again. Io tried to break free of the chains, but was unable to. Both were surprised, as Shun's blazing Cosmo had caused the Andromeda Cloth to start giving off a beautiful golden radiance. It was the blood the Gold Saints had given to resurrect the Andromeda Cloth that had imbued it and its chains with a great new endurance and life force.

Ensuring that Io would not be able to break free, Shun attempted to try to demolish the Pillar himself. Kiki arrived with the powerful Libra Gold Cloth, which held the key to destroying the Pillars. The Libra Gold Cloth handed Shun the nunchaku, and Shun was ready to demolish the Pillar.

In despair, and out of his fierce loyalty to Poseidon, Io tried to stop Shun and did the unthinkable. Throwing himself in the way of the attack that the nunchaku launched when handled by Shun, Io was struck with the full force of the attack with no Scale to protect him. His sacrifice, admirable as it was, proved to be meaningless since the Mammoth Pillar of the South Pacific Ocean was demolished by the attack he tried to stop. With his last breath, Io tried to warn Shun that his mercy would be his undoing, and finally met his end.

Scale
The Scylla Scales represent Scylla, a nymph who was turned into a monster by the immortal sorceress Circe. Scylla rejected the love of a river god, who went to Circe for help to win Scylla's heart. However, when she heard the story, Circe fell in love with the river god and was furious with Scylla for hurting him, even though the river god rejected Circe. Circe proceeded to pour a potion into the lake Scylla bathed in, transforming her into the monster. An alternate story tells of the gods turning Scylla, a princess, into the monster for betraying and indirectly killing her father, Nisus, because she fell in love with his enemy. Scylla killed six companions of the Greek hero Odysseus, in The Odyssey.

Trivia

 * Io shares his name with a maiden in Greek myth. Io was one of Zeus's unwilling lovers; Zeus caught her as she ran from him and violated the girl under the cover of clouds. However, Zeus's wife Hera was suspicious and descended, but Zeus managed to turn Io into a white cow before Hera saw her. Not fooled, Hera forced Zeus to give her the cow and had it guarded by Argus, a creature with 100 eyes that never fully slept. Zeus freed Io by having the god Hermes disguise himself as a shepherd, lull Argus into a full slumber and kill him. Hera, enraged by her guard's death, sent a horsefly to sting and chase the bovine Io around the world, never letting the poor girl sleep. The spell was lifted when she reached River Nile in Egypt; she was changed back into a woman and gave birth to Zeus's son Epaphus.