The trouble began for Baldur when he had a dream (or more than one, I don't know the source material) that he interpreted as foretelling his death. This saddened him and _alarmed_ his mother Frigg to the point that she went through the entire world *making every single entity she found* PROMISE that they would not cause Baldur's death. And I mean everything_--people, animals, plants, inanimate materials...heck, she probably extracted promises from mercury and lead and arsenic not to poison her wonderful son. The entire world was to be Baldur's safe space, because Baldur was so wonderful he deserved complete safety...right?