Complex sentence: She then summons Holo-Pearl, the holographic version of herself introduced in "Steven the Sword Fighter", which spooks Steven and causes him to summon his bubble by reflex, but he soon deactivates it and steps to the side for Connie to start.
Split into simpler sentences: She then summons Holo-Pearl, the holographic version of herself introduced in "Steven the Sword Fighter", which spooks Steven and causes him to summon his bubble by reflex. Steven deactivates it and steps to the side for Connie to start.