The canon story behind this is that this outpost is one of many used by the sand tribe during the Core War. Most of them were scavenged since then, but this one somehow remained intact. In the story, this set would show up when Mata Nui is on his way to save Kiina from the Skrall, and he uses it to defend himself from a Skrall patrol. The actual set would include a Kiina minifig just to have another minifig, since lego sets don't always follow the story exactly.
Anyway, onto the set:
Set name: Desert Hideout ambush
Pieces: 138 (that's accounting for new molds and an actual head for Mata Nui)
open and close the hidden door to reveal the giant Thornax cannon
Run and get Mata Nui's shield
Includes four minifigs: Kiina, Mata Nui, Elite Skrall, and Skrall warrior. Also includes Click
Wait... is that....? Yep, that's definitely a Skrall Shield.
Sorry, couldn't resist.
And that's it, as always, any comments, critiques, criticisms, complaints, or cobras are welcome!