User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-73.46.6.122-20150727181231

Do you think the next volume or a future short story will finally explain what the gremory clan's true special power is other than superior magic control and more importantly why lord gremory, rias, sirzechs, and millicas haven't used it in so long? You think rias will use use it in volume 21? All answers, opinions, theories, and speculations are acceptable. Personally I think their power is similar to that of a succubus's power to absorb power from love, hypnotize/seduce their prey, heal they're "soulmates" stamina, lifeforce, & magic(similar to oppai beam and senjutsu) and even shoot out powerful energy blast(and with female members of the clan they can also shoot out engery blast from their breast like in Rosario+Vampire), hence why they are such affectionate devils because the amount of power they have depends on how much they are loved.