The golden light that was surrounding the egg was warm. It was as if a mother was embracing her child in her arms.
Eden could feel it, and because of that, instead of feeling excitement, he was feeling calm.
And this feeling only accentuated his joy because not every monster could make its 'master' like this. So it means only one thing.
That the monster was an angel.
He didn't know if angels were exactly like what he thought, that is to say, extremely beautiful beings with bird-like wings. But by seeing and feeling this warm golden light, he was sure that it would be something that wouldn't shy away from what he had in his head.
So he waited. He had finished the dungeon anyway, so he didn't have anything else to do.
He could have probably done it another time since he still had quite a lot of times until night-time, but he preferred waiting for the egg. It was better like that.