Reili
I don't think it will be easy for Shiro fight him. And Im afraid he already know all garden secrets and try to create artificial Empress connected to this garden. Otherwise he could continue to improve Arnia. Also, Shiro herself are artificial Empress too, because her origin is from dungeon, not from this garden. Chaos used Kuromi corpse and fraction of the soul to create Empress from simple dungeon monster.
I wonder if it is possible to consider the creation of the second queen in the garden, in violation of the quota, as a violation of the laws of physics or something like that? How exactly did he manage to disrupt the functioning of the system? I think even Chaos would have problems with that. Small ...