What is the oldest living creature in your world?

What is the oldest living creature in your world, and what is thier story?

How/why did they love for so long?

For those in more high fantasy settings, what's the oldest creature that started as mortal?

Just to exclude things like gods or immortals.

In my world, it would be the oldest living elf, who was once a famous philosopher, now turned ultra-nationalist. The last living elf from when there was such a thing as an Elf civilization.

Elves are already naturally long lived in my world, with most living well beyond 1,000 years. Which got further enhanced with powerful advances in medical knowlage, tech and magic.

He's been able to use that old long lost tech and knowlage to make himself age far slower than a normal elf. He's already well over 2,000 years old, and the tech and magic he has will ensure he can live for another 4,000 at least. (Little does he know that none of it matters, reality itself is slowly being undone. He will be lucky to get another 100 years)

He's done this to hopfully one day recreate the destroyed elf civilization, and subjugate all other races and nations.

He believes it's his moral imperative to take back control, and guide all other races and people in the "proper" way to advance.

So how about you? Tell me about the oldest living mortal being in your world?