Defense masteries
When exactly do your masteries lock on your defenders? When you join the war, or when you actually place the champ? Say for example, I want my dr doom to have mystic dispersion, I'd put that mastery on before I place my defense, but I want suicides on my Elsa bloodstone, but not doom. Would I be able to place doom with MD, and then change masteries to put suicides on after I place him to put the rest down with them on, or do they lock the moment you join?