One of the 12 Golden Zodiac spirits who are two twin spirits. They have the ability to mimic any person completely and have made a contract with Lucy after Angel's (their previous owner) defeat.
Gemini's Gate Key.
Little is known about these twin spirits except that they were previously owned by Angel and obediently carried out her orders. But during their battle against Lucy, they were unable to strike her and defied Angel's demands upon learning just how much Lucy loved and cared for her spirits. After Angel's defeat, Gemini (along with Scorpio and Aries) confronted the blonde Celestial mage and generously offered to provide their assistance.
Gemini, created by Hiro Mashima, was designed to properly depict its respective Zodiac sign of two twins. It reflects Gemini in Greek mythology whereby "Gemini" were two twin brothers known as labal and lvbal. However, in the Fairy Tail series, Gemi and Mini are not completely identical in that they wear their sashes in the opposite direction and the shape of their mouths are reversed. The most probable reason behind this was to differentiate between the two spirits.
Because Gemini's dominant magical ability is transformation magic, it has transformed into and took on the appearance of numerous mages and individuals, as depicted in the Oracion Seis Arc.
Gemini can't attack Lucy.
Under Angel's ownership, Gemini displayed little concern or empathy towards their enemies and often executed their attacks in a cruel fashion. For example, they ordered Sagittarius to shoot Hibiki in the back (while transformed as Lucy) and kicked and beat Lucy repeatedly during their battle. But after understanding just how much Lucy loved her Celestial spirits, they've become more caring and kind-hearted. They even as so much voluntarily came to her aid when she ran out of magic to help destroy one of Nirvana's legs. That said, Gemini has still remained the joyful and playful two spirits that they have always been and continue to exhibit great loyalty to their master.
Powers & Abilities
Gemini, transformed as Gray, uses Ice Magic to defeat the original.
Gemini's prominent ability is to flawlessly transform into any person they come into contact with. This includes appearance, personality, thoughts, memories, and powers. However, it has two weaknesses: their transformations last only five minutes and they must touch the person in order to transform. Although they may retain the capacity to transform into two people, additional transformations require them to erase one of the transformed forms. Those whom they have transformed into:
Ichiya - Like Ichiya, they are able to use his perfume ability and have used it against Jura to paralyze him. They also claim that he only thinks about perverted things.
Gray - They can use Ice Make Magic on the same level as Gray's original Ice Make magics.
Lucy - As Lucy, Gemini can use the whip and summon spirits. They also use her attractive body to distract male enemies