Global: Pay bolt and KO one of your character dice. The next die you purchase this turn costs 2 less (to a minimum of 1).
Apocalypse: Wicked Supremacist Global Ability reads:
Global: Pay bolt. Once per turn, KO one of your character dice, and the next die you purchase this turn costs 2 less (to a minimum of 1).
Is making a purchase a requirement to use these global abilities, meaning it could only be used during your main step?