Celestial Spirits are made to be quirky and comical and I don’t mind that to a degree but I’m gonna take a more serious approach. This spirit has so much more potential than just cutting hair, so here I am giving him more abilities and magic¯\_(ツ)_/¯. Also he does not end all his sentences with ‘ebi’ but does call Lucy that.
In ancient times, on another world, a Celestial Spirit descended and became a goddess of that world, drawing power from the moon and water. A few others followed her, and they gathered human followers around themselves. Inevitably, a sense of jealously and competition grew. One of the other gods produced a son that would challenge the first goddess. Fearing destruction at his hands, the goddess put challenges and obstacles before the son, but he fought through them all successfully.
One of her followers offered himself to her defense, and she bestowed great power on him. He went to battle for her, but ultimately sacrificed himself to give the goddess more time to prepare herself. To save and honor her supporter, the goddess helped his spirit ascend to the celestial plane, where he was helped by the Celestial Spirit King and was anchored to a constellation.
Later, he and the Celestial Spirits would venture to Earthland. With an empathic, nurturing nature, he would often be called upon to act as counsellor and peacekeeper, but his reputation as a fierce protector also led to frequent calls for his defence skills. He became known as Cancer, the giant crab.
His attacking magic is Celestial Cuts. Before being a spirit, he wielded twin swords (similar to Lucy’s stardress form of his) and was an expert despite not having a desire to fight. As a spirit, the swords are now scissors, imbued with magic that allows them to cut through almost anything. He is able to transform the scissors into different blade styles, even back into swords, and can deliver multiple slices in the blink of an eye.
His defensive magic is Celestial Carapace. Typically, this magic is an invisible barrier/armour around him that is immensely difficult to break through. As his key holder grows stronger, so too does his defensive capabilities. He can extend this barrier out from himself, (the range potential increasing with his summoner’s own increase in magic ability) or cast a shell around his key holder.
He is also associated with growth and has the ability to accelerate the growth of some things (such as when he grows someone’s hair back). His reputation as a ‘water’ sign comes both from his fluid fighting style and the way a flood of water appears if his Celestial Carapace spell is broken.
The interest and penchant for hairstyling came about in more recent generations, after he saw how much a hairstyle could affect someone. He enjoys helping someone feel good about themselves and prefers it over using his blades for fighting.
He has been connected to the Heartfilia line since the beginning, they were drawn to each other due to their empathic and protective natures. He has always provided them with guidance and helped them maintain connections with the other families.
Cancer presents himself as being cool and even tempered, often hiding any troubles he may be feeling in order to focus more on other’s issues. He is deeply sensitive beneath that and is also extremely caring. He can be quite motherly and overly worried at times which can lead to rare cases of him snapping, but he is incredibly loyal.