Yea I've read the entire series multiple times luckily, (I say luckily because you just revealed a major spoiler!) and sorry for the confusion. I meant that he is "evil" most of the time he appears.
EDIT: re-read your post- and ok that "spoiler wasn't too major
English
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Oh, I get what you're saying. Yeah, it would have been cool if Murtagh and Thorn were with Eragon and Saphira from the beginning.