While it's not entirely clear how the new mode works, this tweet from lead designer Dennis Brännvall seems to suggest it'll be some sort of bounty challenge. Unsurprising, considering it's Jabba.
@r3b3lspy @sledgehammer70 Correct. Much more info really soon. Jabba is coming!March 8, 2016
However it works, it looks like it'll get you new guns with Reddit noting he seems to be offering non-DLC weapons. Specifically that pistol, recently seen in Star Wars Rebels but more famously used by a semi-blind Han Solo to shoot a Sarlac tentacle in Return Of The Jedi.
The other weapon is obviously some sort of sniper rifle but I'm not sure what sort of variant. It currently looks like the DLT-19 heavy blaster only with a scope. Which is worrying...
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