After you arrive at Nortinka, go to the left igloo (the last upper one) and get the key. Kill all of the enemies there and obtain snowballs. As with Goronu, exit Nortinka and then go back again. This gives the enemies a chance to respawn, which lets them drop more useful items (in this case, snowballs). When you have enough snowballs (at least 30), leave Nortinka and enter your next destination, Crater Cove.
Items to Obtain: