According to adsense rules you can't unless you own everything in the video. You didn't make Skyrim so I would say that breaks their TOS
id love an official statement on this subject since almost every single skyrim gameplay video got ads on it, while couple of mine got rejected (i need to provide some kind of info to yt that i am allowed to use ads)
had no single problem about blizzard/black isle etc games, either streaming or youtube, thats why im kind of confused about this adsense rejection, its the first time my gameplay videos got rejected by adsense :<