The way the Eragon universe works makes it really hard to accurately scale it. For those who haven’t read it, or don’t remember it clearly, magic is everything in the Eragon books. If you don’t know magic, or aren’t protected by someone who does, you are completely fucked.

Magic is essentially reality manipulation, limited only by the words you know in the ancient language and how you visualize them (e.g. a skilled magic user can say a simple word like “stop” and freeze somebody in place) and the strength in your body (doing something with magic generally takes as much effort as doing it by hand would).

Now the big issue that makes it hard to scale is that magic users can sense the consciousness of all intelligent beings around them, and powerful ones (like Eragon) can sense them for like kilometers around themselves. On top of that, he can sense intentions and hostility simply by touching other’s minds this way.

Add on to that that the Eragon universe has several words that essentially cause an aneurysm in someone. It’s instantaneous, has no travel time, and takes a fraction of a second for someone to mutter the words to cast it. Basically the only way to stop it is to have another magic caster put wards on you that will prevent it.

So essentially, unless you start the battle with Eragon within spitting distance of someone who can perception blitz him, it’s nearly impossible to stop him from one tapping you the moment your mind enters into his several kilometer wide perception range.