People have suggested Mythical / Mythic before but I'd prefer something else.
I don't know, it's not a horrible title, but it does go along the lines of Legendary in its blandness. There have been threads about this before, but I can't recall exactly what names have been suggested and I don't recall having heard many that I was really enthusiastic about.
If you search 'mythical' in Meta you'll find a few. Think I proposed a couple names somewhere (though I might be getting mixed up with the donator ranks as I remember proposing few names for them).
Turns out it might have been theymos who suggested mythical:
Probably the next one would be "Mythical".
At one point I absolutely thought there probably should be at least one more rank above Legendary, since with time the number of Legendaries would be huge and there wouldn't be much that was special about it. Now, with these merit requirements that are going to have noobs pulling out their hair for years, I'm not so sure about that. Even lower-ranked members who aren't shitposters are having a hell of a time ranking up to Sr. Member or Hero, much less Legendary. At this point a higher-ranked title means more than ever.
New legendaries will be very rare, especially for new users signing up and only the best of best posters will now ever achieve that status. However, there's still a hell of a lot of people who got that rank before the new system and probably a lot of low-quality contributors, and that's why I think there should be some distinction. Maybe we should demote all Legendaries who don't achieve a decent amount of merit because it means very little when all you had to do was be here a while. Maybe remove the airdropped merit from them and they're just a Hero until they've achieved the required merit. Then that rank would mean something.