I stumbled on this one just the other day, it was a great read but I lost the bookmark too.

I cant believe that the horseman survived 3,ooo years being killers all the time

even Caspian would have gotten bored or decapitated before that.

there was a lovely fic where the horseman who are killed aren't really Methos's brothers but other old immortals he and the other 3 manipulate into being there for the showdown.

I loved it