How were the twins connected? Through the Control Orb, of course! Celis and Kentucky were also connected to them through there, but they couldn't do something like use Rean and Roan's Element exchange. Sister Orb, as kind of the spirit of the Orb, could.
She never had a need for it, but she was literally at the crossroads between the twins' connection. Besides, if there was someone who could use the twins' elements as well as themselves, that was definitely Sister Orb... or the system, although the system doesn't seem to have a will of its own to do such a thing.
In any case, Sister Orb immediately intercepted the Light and Dark Element that the twins were sending in her direction. What was attacking the system was pretty obvious: the Dark Purple Energy!
