Demogorgon was a race that had many racial skills. One such skill allowed them to intimidate any member of a lower grade race. This fear was something that was impossible for someone to withstand without a strong willpower. Skills like fear resistance or fear immunity had no effect on it. The name of this racial skill was "Dreadful Intimidation of the Tyrant Overlord".
As the Cosmos Swallowing Worm was a monster with very limited intelligence, it had very few ways to develop its willpower. So it had a hard time blocking any attacks that targetted the willpower directly. So this skill was super effective on it.
