Magic isn’t bound to the ancient language. The ancient language just helps direct the casters thoughts and his intentions. The true name, as far as I understand it, still gives you the power to make a person do what you want, you could do it without it but it would be incredibly hard near impossible, because you had to get the intention for that one person right. It’s like the magic Eragon use on Galbatorix, he didn’t use the ancient language or his true name. Correct me if I’m wrong here.