The Dink Network

Cool down. All you need to do is get some healing potions, the massive bow and powershot. Then it's a matter of hitting Seth well enough end trying to avoid touching him. If that doesn't work you should try better or you're too weak because you're either a low level or you've missed potions. Anyway Seth isn't hard if you have some defence and use the massive bow with powershot on him.

BTW: Hellfire and lightsword barely have effect on Seth. And its better to use the massive bow since the firebow doesn't do powershot.