Viking Batlle Adverse: Effect is too powerful since it allows you to summon ANY warrior from your deck. Needs to be toned down to at best a level 4 warrior or have some form of stat restriction like <1500 ATK or something. Also, no reason for it to be a Counter Trap. It is fine as a regular trap.
Nail: Warriors already have Marauding Captain with this same effect. Having too many cards with that effect in the same type creates too many locks imo. Also, typically cards with that effect don't have such good stats.
Neithen: should either be rfp 1 card and summon 1 card, or you need to make the monsters be destroyed at the end of the turn to prevent the card from being a +2. Anything that automatically gives you a +2 in Yugioh is almost automatically a broken card.
Niclear War: doesn't really feel like it fits the set. Effect is fine though.
Xena: just change her name because we have all heard of Xena, Warrior Princess and the name you have is just too close. =P
Black Warrior Elf: too much of a mimic of Colossal Fighter's effect (and even more powerful!). First part of the effect is fine and he can have a 2nd effect, just tone it down a bit or else I gotta call him a broken card.
And now for the ratings:
Spelling/Grammar/Proper Yugioh Syntax: 3/10 - Need to work more on spelling especially. Lots of spelling errors in every card (even the card names have spelling errors!). Also a few places where the proper yugioh syntax isn't 100% followed but mostly minor mistakes on that end. It's the spelling that really needs a lot of work.
Originality: 8/10 - Overall, looks like a good amount of original thought went into the set.
Pics: 8/10 - Mostly good. Neithen has an ugly white background so he needs to be changed. I just don't like the Nuclear War card's name or pic much at all either.
Balance: 6/10 - A few overpowered cards as mentioned above. Need to tone some of them down a bit.
My Opinion: 7/10 - Overall, not 1 of the most splendid masterpieces I've ever seen but certainly not a bad set. Note that I consider 5/10 to be "average", so I'm calling this "above average".
Final Rating: 6.8/10 - Nice, above average set.
