WARNING: The following contains spoilers for Runaways #13 by Rainbow Rowell, David Lafuente and Kris Anka.
History in the Marvel Universe is an ancient thing that stretches back long before the rise of humanity on Earth. In this mysterious, nebulous (and yet relatively well-cataloged) time period, all manner of strange things were happening on and around our little planet. Prehistoric heroes battled ancient evil. Cataclysms buried entire nations. Gods (and other monstrously powerful beings) fought to the death. At one point, a powerful group called the Elder Gods was corrupted, which lead to a cleansing of sorts. Not much survived, but at least three beings did. They called themselves the Gibborim.
These mystical beings would lie dormant for billions of years before awaking in the modern age, hungry for sacrifices that would fuel their quest to turn the Earth into their own vision of a utopia. They made a pact with six humans who would later go on to become known as the Pride. The Gibborim promised the Pride that, if they served them well (see: sacrificed the occasional innocence bystander) they would be blessed with unfathomable power and a front row seat to the grisly apocalypse, safely behind the splash zone. It didn't work out like that. The Pride's children, a superhero team named the Runaways, thwarted their own parents and the Gibborim.
Though, that last point might be up for debate now.
Runaways #13 reveals that the Gibborim isn't wholly thwarted -- at least, they live on in the form of the Seed of the Gibborim. The Seed of the Gibborim are the children of the original Gibborim (seen above) and, much like their parents, they have one-track minds. Runaways #13 reveals that the Seed of the Gibborim have been tracking Alex Wilder, a former member of the Runaways who ended up betraying the team when they needed him most. The reason for their dogged pursuit? They want to get the band back together. Or, more precisely, they want to create another Pride and start the sacrifices back up again.
Naturally, the Runaways want nothing to do with this plan. Unfortunately, though, they don't have much of a choice. The last issue of Runaways revealed that Alex Wilder has returned to the team, though the reception isn't exactly a warm one. The last time most of the Runaways saw Alex was when he betrayed the team to save his family. Alex would die for his betrayal, but he wouldn't stay dead for long. Those who have seen Alex since his resurrection don't have nice things to say about their former leader. If anything, Alex has become something of a prolific villain since he returned to life, wreaking havoc on other people's lives left and right. He's keeping his streak hot at the outset of Runaways #13, as he has led some kind of dog-hydra monster right to his former team.