What does it mean to be Chosen?
Chosen means that you were there when Emperor Calus gave a gladiator by the name of Ghaul command of the newly formed army,The Red Legion.
Chosen means that you were there when Ghaul led your army to victory after victory...and he gained your undying loyalty.
Chosen means that you sided with Ghaul and his co-conspirators when they overthrown Calus and banished him aboard his Grand Leviathan and into the void of space.
means that when Ghaul takes the Travelers power, you will be among the first to get it.
That's what it means to be a Chosen of Ghaul.