Update 10/22: The leaderboard is now the Onslaught Leaderboard.
I could not find a plain link anywhere in the forums exept for @Cappa s post, and a lot of people seem not to know about this. So, here you go:
https://leaderboards.ageofconan.com/
Nice to know:
If you die at any level (including lvl 80), you are off the leaderboard.
“age” is /played time of the character
The leaderboard seems to update several times a day.
Cool I am on spot one in the level category… with 19 others 
I didn’t even know about this leaderboard.
Not sure how that placement system works because there are probably not just 20 unconquered characters on Crom I guess?
36 at 80 at this time.
It seems you drop of the leaderboard once you die at 80.
Edit: @AndyB confirmed, see first post.
Yeah, I can confirm you will drop even after hitting 80 once you die. I have a feeling they kept things simple when they came up with this and used some already existing field in a table that tracks character deaths. Anything other than “0” or null would mean you have been conquered. They probably would have had to make some additional field or fields in the table or create another table linked to each character in order to be able to track who made it to 80 unconquered, then died. Or at the very least whatever code/script/select is being used to update the board would have had to be a bit more complex even it could be done using other existing fields and that could have caused other unforeseen issues anyhow.
In other words, they kept it simple so they could give us this content, which I appreciate. Simple is better than nothing and it breaths life back into this awesome game.
I can also confirm that the rewards are still there even after you die, even if it’s within a few minutes after hitting 80 - and for me that’s all I wanted anyhow.
I would have been the 8th DT at position 1 one but only showed 79 briefly in position 2, then once the update cycle to the leaderboard hit poof I was gone. I don’t mind but I will say this design does create and inherent inaccuracy in the leaderboard itself. Who’s to say I was actually the 8th DT? How do I know if I was really the 12 and 4 people before me decided do play their toon normally once they hit 80 and poof they dropped, so I perceived that I was 8th to 80, but now someone else thinks they were 8th.
So take the leaderboard for what it is - it tells you who is at 80 and is currently still undefeated but doesn’t truly display everyone who accomplished hitting 80 undefeated in chronological order. It also doesn’t display any toons who died and what level they reached.
Again, I appreciate that they did this at all and for all I know this may be the way they intended the leaderboard for this accomplishment to work. It does accurately show who is still currently unconquered.
Was fun to see my name up there at all and gave me a little encouragement to get through the last level ! 
Is the Age the /played or /born? How often is the data updated?
It’s /played. Not sure how often it’s updated, but should be several times per day.