The Ice People need to fulfill their destiny of cooling off a warm fizzy beverage. They can only achieve this by sacrificing some of their kin in the pools of lava which, for some reason, lay between them and their goal. When an ice person, which looks like an ice cube comes into contact with lava (or similar) it solidifies that lava into solid rock. The next ice person will then be able to use that solid piece as a platform and thus progress further into the level. Beware also of spike pits and air mines.