Acquire the Key of Serpentis, then play level 10-7, "Jokulkyrkja", in Antarctica. Get on the platform with the odd snake sign and it will certainly decrease into a Boss battle. Beat in charge by tossing knives at the crystals on the ceiling in order to break each area of the dragon platform you are riding on. After in charge has actually been beat you will certainly unlock Antarctica for all characters, Jim Hawkins, and the alternate ending.