The gods are real. The average person in this modern world may not know it, but every pantheon that's ever had some major place in history exists, even people who were not necessarily gods, but embodied a particular concept (such as Uncle Sam). The enemies of the gods, the Titans, have returned. The gods are too weak to fight these primordial gods on their own, so it's up to the Scions, the children of the gods, to help.
Scions are the epic heroes of the modern world. Half human, half god, the world at large doesn't truly know of their nature, and if they're told, they may or may not actually believe it. But what the world does know is that things are changing. There are epic battles in public streets that the government still tries to explain as movie shootings or gas leaks. Strange phenomena happens everywhere. Spectres, titanspawn (the children of the Titans), vampires, goblins, all sorts of creatures exist, and many side with the Titans and offer them aid in exchange for power.
It's up to the Scions what path they choose to take. Different gods and pantheons have their own particular goals in this war, and not every Scion wants to live up to or follow those goals.