A Golden pillar

So they decided to seal the entrances and exits of this world, which was only a temporary solution that would allow them to gather their strength.

And when Diana would have managed to break the seals, because with the knowledge she possessed she would succeed to undo them sooner or later, they would attack them before they decided to invade other worlds.

Thanks to the information they had gathered in the laboratory and in the underground base they had learned a lot more about their plan, which worlds they wanted to destroy, which worlds they wanted to conquer and he had to admit that Diana hadn't been the Goddess of Strategy for nothing.