WARNING: The following contains spoilers for Empyre: Fantastic Four #0, by Dan Slott, R.B. Silva, Sean Izaakse, and Marte Garcia, on sale now.
In Empyre: Fantastic Four #0, Marvel's first family learns that the Kree and Skrull civilizations have made peace after centuries of war. The Kree and the Skrulls both debuted in Stan Lee and Jack Kirby's Fantastic Four comics in the 1960s, and their rivalry has been part of the fabric of Marvel Universe since then, even taking center stage in stories like 'The Kree-Skrull War."
More recently, those two ailing empires are untied under the crown of their mutual heir to the throne, the former Young Avenger Hulkling. As the Fantastic Four is traveling through the Marvel Universe, their ship essentially runs out of gas, and they find themselves at the Casino Cosmico, an intergalactic casino. After arriving there, the team learns that there's been an intergalactic economic collapse. They also realize that the Kree-Skrull War is still playing out within its walls in miniature.
With no money, and little else of value, the team agrees to franchise out the Thing's fighting prowess at the Casino Cosmico. That's where they find that the fights are staged by a new Elder of the Universe, the Profiteer. She's taken over the casino from her brother, the Grandmaster. While Grandmaster represents the impulse to play, Profiteer is the embodiment of greed and money-making. These games that she's staging help cover her lost income now that she's not able to sell war materials to the Skrulls or the Kree. Her games, though, keep the war alive, at least in the hearts and betting tickets of her customers.
The fight pits a Kree warrior against a Skrull, with the area shifting to re-create famous battlefields from the war. The combatants are bloodthirsty and their efforts are nearly deadly. However, the Profiteer's people tend to whatever wounds are incurred on the battlefield. The fight must go on, of course, because there's just too much money involved for them to stop.
The Thing and the Human Torch are in the audience for the next fight when Ben realizes the combatants aren't grizzled warriors at all. They are children, raised by the Profiteer to play their part in her war games. The Thing is outraged, and he storms into the area, dragging Johnny with him. The heroes have every intention of pulling their punches before they realize how skilled, and bloodthirsty, the pint-sized gladiators actually are.
At first, the Profiteer is incensed at the interruption, but she eventually realizes new bets can be placed given the changing situation. Where there are new bets, there's new money to be made.
Ultimately, the Invisible Woman and her two kids, Franklin and Valeria, save the day by attacking the Profiteer where it really hurts: the pocketbook. By winning enough money from the casino floor, they end up essentially owning the facility, which they trade for the young Skrull and Kree's freedom. Because they were conditioned to hate each other, the two still harbor the legacy of animosity that's based around the eons of conflict between their peoples. While the conflict between the Kree and the Skrulls has only occasionally encompassed Earth's heroes, this rivalry once shaped the better part of Marvel's cosmos.
While the Skrulls and Kree joining under one banner isn't new information, they present a unique, overwhelming threat to the rest of the Marvel Universe. Now, the Kree/Skrull armada is quickly approaching Earth -- alongside the Fantastic Four -- and they seem set to show the Cotati aliens and the Avengers just how dangerous these two alien empires can be when they stop fighting.