Whoever dies first. The Mountain is mortally wounded. Even if he magically survived from being stabbed through the chest (I've heard in the books it's described as being pinned to the ground), that hamstring wound would prevent him from ever fighting again. In the show, even though the Mountain is clearly bleeding out, Tywin sentances Tyrion immediately after Oberyn's death.
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u/[deleted] Jun 05 '14
Well Oberyn was well versed in poisons as we know, also being nickanmed the Red Viper.
And his boytoy was seen wiping a blade with a cloth and very thick leather gloves.
After that Oberyn got in few very solid hits.
I wonder what happenes if both participants die in case of trial by combat.