User blog comment:Master Sima Yi/Assassinews 19-03-'14 – Two Assassin's Creeds for 2014?: Unity and Comet/@comment-4786308-20140611082719/@comment-3046679-20140612125605

Not just the color, differently shaped designs are also available.

Which got me thinking - they say in co-op, you always play as Arno, and the others are shown as the three other Assassins. BUT that raises a question - are these in fact actual characters supported by the story, or simply customized Arnos of other players, that virtually have no impact on the story itself, and are just phantoms that help you out?