"Hey, you only hear the endless screaming in Tartarus! And the light from the molten lava of the River Phlegethon is quite charming, I think. Well, when it isn't flooding. Usually charming!"

So, perhaps Zagreus's standards of 'gloomy' are very, very different to Percy. This was someone who was currently wearing several skulls, after all.

Indignation about these baseless attacks on his home aside, Zagreus smiles when Percy asked if he found his mother. "I did. And...she's come back home, too. For most of the time, at least. When she isn't visiting Olympus."