If Frost Walker becomes the target of a spell or ability, its ability triggers and is put on the stack on top of that spell or ability. Frost Walker’s ability will resolve (causing it to be sacrificed) first. Unless the spell or ability has another target, it won’t resolve as it tries to resolve for having no legal targets.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.