Ethereal Fairies

The Ethereal Fairies are extremely powerful Fairies who live out of Time and Space.

Personality
Despite being similar to Arcadia in appearance and powers, they have more austere personalities and have rarely been seen smiling and were never seen joking though it might have been because of the serious situation when they first appeared.

History
The Ethereal Fairies first appeared when they went to give the Gifts of Destiny to the Winx to help them face the Major Fairies of Earth since Believix is powerless against the power of the Major Fairies which comes from Nature and from the Earth itself. They presented themselves as magical creatures who are eternal, powerful as well as being pure, and as existing since before the dawn of Time, timeless and being made of pure energy in the Nickelodeon dub. When they were first appearing to the Winx, Nabu mentioned their magic as being impenetrable and delicious, and ancient and powerful in the Nickelodeon version.

It is supposed the Ethereal Fairies are magical beings who have been existing in the same state and with the same appearance since ever they came into existence because they are described as being existing outside of Time and Space, and they call themselves as being both eternal and pure, meaning that they had been existing since ever alike to Arcadia, and that they are probably made of pure magic, not of flesh and blood like normal fairies such as the Winx. In the Nickelodeon dub they said that they were made of pure energy.

This also means that they were probably some of the first Fairies of the Magic Dimension, and were probably created shortly after Arcadia's birth (since Arcadia is the first Fairy to have existed), possibly by the Great Dragon or by Arcadia. Since they exist out of Time and Space they will continue existing for ever and are hence immortal, and that they are some of the most powerful fairies existing, even if the most powerful fairy is supposed to be the Fairy of the Dragon's Flame (currently Bloom).

Fairy Form
It is therefore very unlikely that Ethereal Fairy is the true final Fairy Form as some fans have speculated, since according to what Miss Faragonda stated in Season 3, Enchantix is the final Fairy Form. Also, as she said in Season 4, there are many higher fairy levels which can be accessed by Enchantix Fairies including Believix. This implies that Enchantix remains the Final Fairy Form, while Believix is only one out of many Higher Level Fairy Forms that also include Harmonix and Sirenix.

This therefore means that Enchantix is the Final Fairy Form, not Ethereal Fairy. As the Ethereal Fairies themselves said, they have always been existing, out of Time and Space, and therefore have always been existing in the same way and have never been normal fairies, and normal Fairies cannot become like them.

Season 4
In Season 4, they came to help the Winx against the Earth Fairies' revenge, saying that it was the destiny of the Winx to defend Earth, and that it was the destiny of the Ethereal Fairies to help the Winx. They gave the Winx the Gifts of Destiny, that are evolutions of their Believix powers, to fight the Major Fairies, because Believix is powerless against the power of Major Fairies. They also warned the Winx of dangers they would have to face, and predicted that someone might lose their life, without specifying who, when giving the Gift of Darkness to the Winx.

Blue Fairy
She gave the first Gift of Destiny, the Gift of Wisdom. It gave the Winx a new transformation, Sophix, to face Diana, the Major Fairy of Nature.

Green Fairy
She gave the second Gift of Destiny, the Gift of Courage and heart. This gave the Winx a new transformation, Lovix, to face Aurora, the Major Fairy of the North. The Gift of Courage gave the Winx bravery and strength, along with fearlessness.

Orange Fairy
She gave the third and last gift of destiny, the Gift of Darkness, which was a powerful spell that could save a person from death once. Aisha tried to use this gift to revive Nabu, but Ogron purposely knocked the gift aside so it would revive a flower instead.

Magical Abilities
The Ethereal Fairies are very powerful creatures and are made of pure magical energy. They are timeless, that is immortal, and have always been existing since the beginning of Time, and were maybe born shortly after Arcadia, who is the first Fairy to have ever existed. They can travel from dimension to dimension and can exist out of time and space, as seen when they appeared to the Winx when they were traveling through an interdimensional portal from Aurora's Frost Tower to their lounge at the Love & Pet.

The Ethereal Fairies are the guardians of many magical powers and spells, such as the Gifts of Destiny.

Since they exist out of Time, they also know what will happen in the future and can warn the beings they are supposed to help. The Ethereal Fairies were destined to help the Winx, who themselves were destined to help the Winx defend the Earth from the Wizards of the Black Circle and from the Vengeance of the Earth Fairies.

Similarities with other all-powerful Fairies
The first magical creature similar to the Ethereal Fairies who appeared in the series was Arcadia, who probably inspired the design of the Ethereal Fairies of Season 4, since Arcadia and the Ethereal Fairies have many similarities, including the fact that they are almost all-powerful fairies and that they are all supposed to exist out of Time and Space. It is to be noted that their appearance is similar to that of Daphne, Bloom elder sister, who was a Nymph (the Nymphs of Magix were nine all-powerful fairies who controlled the fate of the Magic Dimension after the Great Dragon disappeared). It is therefore probable that the appearance of Arcadia and of the Ethereal Fairies was inspired by Daphne's appearance.

Trivia

 * In Greek Mythology, Aether is the personification of the Heavens, of Space and of the Upper Sky. He is one of the Protogenoi, one of the first-born Gods of the Universe as well as an elemental God. He is the brother of Hemera, the Goddess of the Day, and of the Moirae or Fates, the three Goddesses who controlled the Fate of all beings in the Universe. Aether is the son of Erebus, the God personifying Darkness and Shadow which filled all the corners and crannies of the world and of Nyx, the Goddess of the Night. Aether and Hemera are the parents of the Goddess Thalassa, one of the primordial deities of the Sea and a personification of the Mediterranean Sea. Through Nyx, Aether is also the brother of Momus (Blame), Moros (Doom), the twins Thanatos (Death) and Hypnos (Sleep), Charon (the ferryman of the Underworld who made the Dead cross the rivers Acheron and Styx which divide the World of the Living from the World of the Dead), the Oneiroi (Dreams), the Hesperides, the Keres (death-spirits), Nemesis (Retribution), Apate (Deception), Philotes (Friendship), Geras (Old Age) and Eris (Strife).
 * Aether was also the name of the substance which was considered by the Ancient Greeks as one of the Five Elements making the Universe, being the celestial element while Earth, Water, Air and Fire were considered as the terrestrial elements. was thought by them to fill the regions above the Earth's atmosphere and to be what space and most celestial objects were made of. It was thought to be the medium in which the Greek Gods lived.