The characters that will be reacting are the following
Ivar -season 6
Bjorn -season 6
Ubbe -season 6
Hvitserk -season 6
Oleg -season 6
Floki- season 6
Heahmund -season 5
Sigrud -season 4
Ragnar -season 4
Aslaug- season 4
Lagertha -season 6
Harald -season 6
Rollo -season 6
If you want a character and its not in the list comment
