Is it breaking the rules when an orc agrees to do 1v1 PvP against a dwarf, agreed OOCly, then when the fight starts two other orcs assist the 1 orc, killing the dwarf in a 3v1 battle?
It would kind of depend... If it was never specified in a 1v1 PvP match, then there could have been some misunderstanding. However if it was specified as in it was said "This will be a 1v1 match", then yes i'd assume it is.