a funny thing i just learned about dark worlds,
when they are discarded by a cost you don't get the darkworlds effect because it state that if "it was discarded by a bard effect" cost is not really a card effect it is something to activate the card effect , for example lightning vortex or raigeki break, it state "discard 1 card." then the effect will apply for it to destroy
you guys see what i mean, i was just looking at lightning vortex ruling with dark world grapha when i noticed this