The computer doesn't know how to use Rune spells correctly. It's difficult to fight against a human player who knows how to play Gnomes effectively. And, of course, Lesser Demons aren't as dangerous as neutral creatures like Cyclops or Elder Dragons because of their low speed and initiative. But in a final battle, as part of a hero's army with a large number of units on both sides, they will reach you! You can be sure of that! And then it will be bad...