Kinana "Cubellios"

Unlike most other members of Fairy Tail, she joined the guild as an employee rather than as a Mage. When she was young, she was turned into a snake by an evil wizard. She was turned back by Makarov after the master realized that she was actually a human. Kinana had no recollection of being a snake when she was first turned back, but recently her memory as a snake has slowly resurfaced, in which she hears a voice asking to hear her thoughts.

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The person calling out for her is actually Cobra and she used to be his snake.