I Became a Living Fossil at Hogwarts

I am not the protagonist of the era, but I have my shadow in the legends of the protagonists of every generation. I once taught Newt how to appease the rampaging Thunderbird, and I also drank with Dumbledore at the Hog's Head Bar and lamented Grindelwald's ambition. I witnessed the rise and fall of Voldemort, and I also watched Harry Potter become the savior. They are the waves of the times, and I am the long river called time. Every deep sleep is a thousand-year appointment with nature. When they all turned into the dust of history, I was still the new student at Hogwarts. It wasn't until the real crisis of world destruction came that everyone realized that this witness throughout ancient and modern times was the last patron saint of the magical world!