I like the sound of it.  Ancient after thinking does kinda make the account sound old not special. Mythical has kinda a more magical sounding.

I can only wonder what activity for it would be.   You would have to have it very high to make it so special.  I like the random factor to, so random just so high very few would ever get it.  I think it would be fun if only a handful ever got it the activity level was so high.