Blizzard has changed the criteria for entering the “Delve Hall of Fame”. To enter it in Season 2, all you need to do is to defeat the new nemesis, Azta’rec, in ?? difficulty during the first week of the season.
This is a stark contrast to the Season 1 variant, which required you to be within the top 4000 characters in your region for 
Fabled Let Me Solo Him: Nullaeus. This restriction led to a literal race to obtain the achievement, with every region filling up in the first day.
We don’t have exact details about the fight, but it is important to mention that the achievement requires you to solo Azta’rec. Completing ?? difficulty during Midnight Season 2 will also reward you with the Apophic Soul Crusher mount.
