A mature red snake. . .
When it was still a snake egg, it was given to Hagrid to take care of, and after it hatched. . .
She met them at Hogwarts when she reached school age. . .
The Philosopher's Stone, the Chamber of Secrets, the Horcrux, the Goblet of Fire... Are waiting for her.
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The characters are ruined, so don't enter if you don't like it. . .
(In other words, it's a bit like the Legend of White Snake...)