Two Blue keys:
When facing the final boss, Tomator use Baleog when you get to Section 2 (Using Baleog to get past Tomator). Shoot Tomator as he is falling down to Section 3 (using Erik to get Tomator). When you get the "Blue Key", two of them will appear in your inventory. Note: Section 1 is when you use Olaf. Section 2 is when you use Baleog. Section 3 is when you use Erik. Section 4 is when you use all the Vikings.