In beowulf why is it that grendel did not dare to touch the kings throne

In the binary (good vs. evil) epic world of Beowulf, the king is a defender of law and order, and Grendel is the villain who challenges these principles. But neither the king nor Grendel act on their own. The king is God's representative on Earth and a protector of all his subjects. On the other hand, Grendel is not an ordinary villain or a monster. He is the descendant of Cain, Biblical figure who killed his own brother. As a creature of hell, he mustn't touch the king's throne, which is God's endowment. In other words, the one who symbolizes the Devil must stay away from God's symbols.