How about this guy? How old is he? I feel like he might have outpaced Divayth Fyr.

Oh my friend, many characters in Dawnguard were older than Morrowind's Divayth. Gelebor, Serana, Harkon, all of these people are thousands of years old. I am not entirely sure on the exact age of Gelebor though. But Serana preceded the unified Empire.

So does Fyr. Fyr has been around since before recorded history.

Serana's not necessarily older than Fyr. As far as we know, she might have been born between Borgas and Reman, or during the Interregnum. She's not older than Solitude, for one. Also, bringing vampires into a wow-this-guy-is-old contest is cheating something hardcoe.

Edit.

It was a mention of people that is old-as-hell. I did think Gelebor is older than Fyr, though.

Gelebor is implied to have been around since the initial fall of the Falmer, isn't he? That would make him very old indeed. I might be mistaken, though. At any rate he claims to have been watching the Betrayed and his Shrine for hundreds of years.

Divayth Fyr is well over 4000 years old. When was the Night of Tears and the return of Ysgramor, exactly? I'm guessing around a little over 4000 years, as well. They might be pretty close in age, actually.