It wasn't all bad news. While Dante might have been 'tricked' into registering for the Eternal Universe battlefield as one of its combatants, it also granted him access to the vast resources and benefits that came with this area.
However, that was one thing. Another was the fact that the Eternal Universe might think they had outsmarted Dante, but if Dante had already known all this, he would still have chosen to register with the Eternal Universe.
What a joke. His home universe was currently his backyard that he was steadily conquering to expand his power. They were fortunate enough to be considered a 'baby universe', thus exempt from participating in the Universe Battlefield.