I've been invaded three times on my character in DS1 and they've all been by seemingly unkillable players, this last one especially, he got one hit on me with his sword and it brought me down to almost unseeable health. I hit him three times before that with my club and it did nothing, he started toying with me after that and I couldn't do anything. I'm getting really sick of this, are they cheating or am I doing something wrong?