The Maddening Roar
The party all bears identical aberrant dragonmarks, obtained when they were overtaken by the mists rising from the destruction of the nation of Cyre. Arik Redtree also bears the same dragonmark, as he was also present at the same location as the party members when Cyre was destroyed.
Each aberrant dragonmark provides its bearer with a different ability, but they all look identical. Fortunately for the party, the aberrant dragonmarks are in easily concealed locations, for those bearing aberrant dragonmarks are often looked upon with suspicion or even outright fear or hatred, due to lingering emotions from the War of Mark several centuries past when the twelve established dragonmark houses fought and destroyed an army of individuals bearing aberrant dragonmarks.