He frightens the sun and eventually will catch her

There are two wolves, and the one who is chasing her [the sun] is called Skoll. He frightens her and eventually will catch her. The other is called Hati Hrodvitnisson. He runs in front of her trying to catch the moon. And, this will happen.

...

Next will come an event thought to be of much importance. The wolf will swallow the sun, and mankind will think it has suffered a terrible disaster. Then the other wolf will catch the moon, and he too will cause much ruin. The stars will disappear from the heavens.

S. Sturluson, The Prose Edda, tr. J Byock (2005), 20 and 71