Edit: New information has been posted, check July 2014
This is very bad, and disheartening indeed.
As much as I love ALLSTAR for making Wild Frontier, I am horrified to explain that it is INCOMPLETE. (In a bad way too..)
When you defeat Diablo, watch the cut scenes and text, with the credits flying by, and receive the next and last mission. It is one you can not complete due to ALLSTAR's failure to allow Hell Mode activate.
What was suppose to happen, once you speak to Moking in Cemal, you will active Hell Mode, wether it changes the difficulty in the game you are playing currently, or be able to select from creating a new slot/file. Now the other question was the missions, if you have to start back at the beach, possibly with all your armor, or find your armor later, and Puppy's level being anywhere from normal 7 to 57. (Since it be twice as hard...)
I am now going to press more attention towards contact with ALLSTAR.
Edit: Any attempts to contact them leads to no reply, my apologies..
With some better news, this guide will not stop, I will continue to update as I play around.