Bubby: I look up to hear Alpha's yell echo. Everyone else does too. I conjure two backwards-held assassin blades of Shadowflame.
Mezmera: Seeing Bubby rush off, I conjure my battle axe and follow her.
Xana: Seeing that the area is in danger, I stop what I'm doing, conjure a whip made of lightning, and follow my sisters.
Spazmatism: Hearing Alpha, I fly out of my position and motion for Retinazer to follow.
Retinazer: I obey my brother, flying with him to follow the three sisters from the side while he watches from above. (Just so happens to be the same formation the actual Twins battle is fought in, but reversed)