The Void is an ever-present threat in League of Legends lore, with Runeterra being made specifically to combat it. With some recent stories, Riot are teasing movement on exploring that storyline.
Screaming into existence with the birth of the universe, the Void is a manifestation of the unknowable nothingness that lies beyond. It is a force of insatiable hunger, waiting through the eons until its masters, the mysterious Watchers, mark the final time of undoing.
The Void has taken root in quite a few regions of Runeterra, from the broken lands of ancient Shurima, to the frozen wastes of Freljord. It has remained as such for quite some time, but recently, with the release of Sejuani and Malzahar stories, this may change.
The lore of Freljord is one fraught with conflict amongst the various tribes, fractured after the betrayal of Lissandra. These tribes seek to either subjugate or assimilate others into their ranks, and there is no love lost between them. The recent Sejuani storyline points in the direction of banding against a common enemy, and presenting a united front, and who can that enemy be but the Watchers, entombed in ice.
In the recently released Malzahar story, the protagonist is fed to an impossibly large void creature, and in the moments before his doom, he glimpses the fall of the Immortal Bastion, Noxus' capital, and Freljord engulfed in chaos as the ice ruptures, and grotesque creatures come pouring out.
It is likely that this is a teaser and the setting of the stage for an event in League of Legends' near future, where Runeterra finally, openly, confronts the Void threat.