The wall of mages

"That red line, the castle is being attacked".

"What?" I exclaimed. "It's being attacked by what?"

The castle was considered impregnable to almost all forms of attack.

In fact, I first asked Dan what would happen if the castle got breached, he laughed heartily.

"The castle can never be breached". He said through the laughter. "It can't even be attacked".

"Why can't it be attacked?" I asked him, confused.

All that was needed was for the beasts to spawn somewhere close and they would attack the castle.

I believed the main reason the castle hadn't been attacked yet was because the beast army was probably stretched too thin.

It wasn't easy to attack different parts of the empire at once and a great number of beasts are needed to over power the mages.

So it made sense that there weren't enough beast monsters to lay seige on the castle.

It was why I assumed the castle hadn't been attacked yet.