Treasure Bags on Stronghold
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Beer Steins on Siren Belch
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DNA Vials on Transit
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These vids show you how to get the many hidden items around you on the maps. It's best to do this on Beginner/Long Solo, with yourself being a level 6 sharpshooter and switching to Beserker. Also you might wanna press shift-tab while in game, open up the web browser, play the vid at the same time, and pause and go. That's how I got the achievements. There are three in total. Good luck :d
-Mandalor