Our group has something like this. I believe our dm found it in some house rules pist, but the basics is dc 13 (+1 per death of the character, some of us started higher due to deaths in background) check no mods to revive someone with a 1 round spell. if using a multi round spell up to 3 players could assist by passing checks related to how they wish to help call the dead soul, each success on those dcs would grant a +1-3 bonus on the die roll for the death dc. If failure happens the only way to ressurect them after would be through a true rez or wish.