Looking for a Nord style fantasy series from the mid to late 80's

I read this when I was a kid and now I can't find it. It had names like "The Troll and the..." and so forth. I think there were 4 to 5 books. It was heavily Norse and in the first book the antagonist went into a barrow and came out in another world. A whetstone was mentioned thrown over a troll, a silly magician became more powerful through this series. Anyone know the author, name of the books? Anything? I loved it as a kid and I need the nostalgia kick. I can't think of anything else right now, the antagonist was relectant and hated by the female character but became strong. Classic hero journey. Shlocky, but the Norse stuff was cool.