Here is a short guide on how to obtain the Ascension, the Legendary PvP back item:
https://www.youtube.com/watch?v=S6Ecrj4GPf8
In addition to the back item, players also receive a glider skin.
http://wiki.guildwars2.com/wiki/The_Ascension_(glider)
This can be done by the average player. I've played three seasons so far and theoretically could get the Ascension this season. Realistically, I'm looking at the fourth season as that would also give me time to get the materials for the Gift of Fortune.