Another problem - Krogh

I don't seem to hit him. The first time I played the game (ages ago), I killed him. But now I don't have the memory of this at all.
Now I even have the Exhausted Witch with me, but only 4 Rune Tablets. Not even the Magic Sword can hit Krogh. There's something cycrling around him, and he kills me in a minute. I use healing every time, and my physical energy is full, but my warriors simply don't hit Krogh. Any help?