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Dragonslayers are powered by emotions. After just heartlessly killing Sting's best friend in front of him? Yeah, I'm not sure anyone could take that blow.
Cough*Hades*cought

Also, had he been worth the title of GM he would newer have let it connect in the first place.

I think Guilds have some leeway and I can't help; but think the smirking chick from ST will say something like "In ST a member can challenge the Master to a duel to death for the leadership, and you can also choose someone to fight in your stead. I challenged Master and asked Sting to fight for me"

Or perhaps I am sleep deprived and only make sense in my head.
Whatever internal rules ST might have doesnt matter when they break the rules of the kingdom, and i am pretty sure they have rules about killing your own guild master.