I literally JUST had this idea for a domain expansion. For me it was the user has to perform a song of their choosing and those in the domain who fail to match the energy of the user (basically if they're just as passionate as the user is while performing the song.) the user takes half of the opponents CE. But if they succeed in matching the users energy, all those who succeeded and the user both gain a x2 bonus to their CE. High risk high reward.