Using the Jolly Rodger, Space Normalizer, Short ranged weapons and Inferno plates is a excellent combat combo if you can also have a decent bit of armor, cargo, and healing stuff. Its what I use to utterly own pretty much any ship that crosses my path to a extent. Of course you do end up spending some time repairing your actual hull unfortently once you get so far.
To open up the Ruins of Manehatten you need to defeat the Ultra Sentinel who is behind a boss door somewhere in the abandoned stables. Once you beat him you can open up the forcefield that is in the exit room of the Stables. That's as far as I am currently and I don't think their is a place beyond the Ruins of Manehatten but I could be wrong.
To open up the sewers you need to beat the raider boss that is in the factory somewhere behind a boss door. After you beat him find a exit and go to the locked armored door in their and open it to get into the sewers. To go past the sewers you don't need to defeat any specific bad guy you can proceed to the abandoned stables beyond the exit. Make sure you have a anti-rad suit if you go through the sewers since some parts are flooded which means radiation galore.
The spell Deformation Wave that unlocks at level 16 is a VERY good spell for just about any situation and it can even bust down most walls with like 4-5 shots! Deformation wave counts as explosive damage to anything it hits so its quite powerful against most foes and it can even work underwater!
LOL! I found that you can trick the dragon into roasting the Yeti if you dig out and time your dodge of the flames just right! Poor yeti got Barb-qued XD
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Thank you!