I don't believe anyone has talked much about the Skulls of the Shogan rewards, but i figure I'd post a bit about them in case anyone wanted some tips:
Devil Inside
You will likely get this just playing through the game, as all it requires you to do is turn your general into a demon by eating three enemy skulls. You can do this as early as the first level.
Were you using that?
Another one you should get just by playing, this requires you to haunt an enemies fox shrine, which you can do during the first level after you pass the first gate. Just let them haunt a shrine then go over and take it.
Outfoxing Death
You'll need to first haunt a fox shrine, and then turn that fox into a demon by eating three enemy skulls, after which you unlock the ability to revive fallen teammates. Just walk over to a friendly unit's skull and you can revive them using 100 rice (so make sure you don't spend it all first). It sounds a bit more complicated than it is, as unless the enemy is aggressively eating your skulls you should have enough leeway to get over to one and revive it.
Web Master
You just need to win an online match to get this one, which is super easy if you have a friend to play with who can just let you walk up and kill your general. Otherwise you'll just have to be good enough at the game to win legit, though I don't know how many people are actually playing online. I'm happy to help people get it, so if you've already got me added on Steam send me a message and I'll help you out (does not apply to lurkers).
The Bone Collector
This is unlocked by earning 15 golden skulls in levels, which you get by completing special objectives (of which you can do 3 per level). There's no real strategy for this as each level has unique challenges, but I would just recommend going for one or two per level instead of all three, as some are really difficult if you're trying to get them together and others actually force you to replay a level multiple times to unlock them. There are 75 or so skulls total in the game though, so even if you only get 1-2 per level it shouldn't be too hard to get 15 eventually.
Hopefully this helps someone, though the achievements are mostly self explanatory. Either way I'm glad I took the time to check the game out again, as I'm actually enjoying it a lot more than when I first tried it and will definitely be playing more of it.