While the Earth's Core wanted to leave and escape, Eric had no intention of letting that happen.
After all, this was the great opportunity he had been waiting all this while. If the Earth's Core had shown itself in a different way, it would have been difficult for him to defend.
But this way was actually what he wished for the most. That was also the reason why he had actually picked up the Hidden Phoenix and pulled her with him.
Now he had the upper hand though, as it would be a battle of two against one, even though the second person on his team was negligible.
Despite that, as long as his supporter was alive it was a good assurance that the Earth's Core wouldn't be able to achieve what it wanted to do.
It was precisely with such thoughts in mind, that Eric immediately called his 4 Clones in the Soul Space of the Hidden Phoenix and attacked the Earth's Core Avatar in there.