I realized that the Khyber crystal is for a Death Star. I was just wondering if there will be more super weapons in the Sequel Trilogy.
Regarding Maul’s lost arc …
[spoil][align=left]
… you can read summaries of the comics at Wookiepedia:
The books reveal that Maul is Mother Talzin’s son. In the past, Sidious promised to make Talzin his apprentice. Instead, he absconded with some of her dark secrets and her child.
At the end of the arc, Talzin is killed by General Grievous. However, Maul lives. Apparently, Sidious isn't worried about future threats from Maul.
Maul’s survival makes the prospect of a standalone Obi-wan film more interesting. Since Kenobi destroys Grievous, are the two even Steven in Maul’s mind? Would Obi-wan compromise his beliefs and mission to protect Luke if an opportunity to end Maul’s life presents itself?[/align][/spoil]