Yes, Bjargsig Cliffs (map S5) is unlockable. It's tied to a Freyja quest, I believe, though I cannot recall the quest name or requirements off the top of my head. Go to Asgard and click on the Freyja statue to see what is next if you offer her enough Chaos. I think perhaps you need to upgrade her barracks. Let me know if you figure it out. If not, I'll dig a little deeper for you.
I was really enjoying the game but then I unlocked that ship-shop that lets me buy stuff for currency earned from having friends... oh no... I hate those things. Spirit could also refresh a bit faster.
Heh :) Glad to hear you're enjoying the game! The ship-shop (Trade Emporium) is just another way for you to get/create items and units. You don't need to use it if you choose not to interact with your friends. You can get most of the same items and units by just playing, through Garrison Tribute, and/or you can purchase items and units.
UPDATE:
Viking Raiders has been updated (Feb 20 2014) ... we've 'de-facebooked' the game, and have removed the timers for recruiting units and for energy (Spirit). Give it a try and let me know what you think!
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Yes, Bjargsig Cliffs (map S5) is unlockable. It's tied to a Freyja quest, I believe, though I cannot recall the quest name or requirements off the top of my head. Go to Asgard and click on the Freyja statue to see what is next if you offer her enough Chaos. I think perhaps you need to upgrade her barracks. Let me know if you figure it out. If not, I'll dig a little deeper for you.