'Vikings' season 4 episode 17 spoilers: The Great Heathen Army gathers; will Lagertha survive the current season?

After two of the older main players have gone to Valhalla, is Lagertha (Katheryn Winnick), newly reinstated queen of Kattegat, about to go next?

Lagertha knew the risk she was taking when she let Aslaug's (Alyssa Sutherland) sons live. Now that Ivar (Alex Høgh) has come home and is openly making threats on her life, her decision to show the cripple mercy may well be the death of her, especially after The Seer (John Kavanagh) has confirmed what she has probably always known: she will die by the hands of one of Ragnar's sons. But which one?

The next episode of "Vikings" season 4 could feature the beginnings of the Great Heathen Army as Viking warriors start gathering in Kattegat. With the news of Ragnar's (Travis Fimmel) passing now widespread, it is up to his sons to uphold his legacy and avenge his death.

In the trailer for the next episode titled "The Great Army," Ivar seems determined to end Lagertha's life and asks his brother, Ubbe (Jordan Patrick Smith) if they were going to allow their mother's killer to escape her punishment. Ubbe says no, and Ivar replies, "Why are we waiting?"

Is Lagertha's life in danger? Or will she be spared for the valuable assistance she could provide in the brothers' quest for vengeance? Will her own son Bjorn (Alexander Ludwig), and Aslaug's second son Hvitserk (Marco Ilsø), make it back home in time to join his half-brothers' raiding party?

The much-celebrated Great Heathen Army was a large coalition of Viking raiders historically recorded to have been led by three of Ragnar's sons: Ivar, Hvitserk, and Ubbe. The army was believed to have been formed following the legendary Viking chieftain's death, and Ivar is generally believed to have been at its helm.

In an interview with Variety, actor Høgh said that his character Ivar's greatest weapon is his intelligence and military strategic skills, and that even though viewers may not see him on the battlefield wielding his sword and slaying people, he would find his own way of spilling blood from his perch.

"He'll be the one standing on the hill organizing, which is also pretty cool, I have to say," Høgh shared.

"Vikings" season 4 episode 17 will air on Wednesday, Jan. 11, at 9 p.m. EST on HISTORY.