Lagertha might appear as one of the invincible characters on "Vikings" but the Queen of Kattegat already knows how she will die in the History series. The Seer has already predicted that she will be killed by a son of Ragnar Lothbrok.

But which of Ragnar's many sons will ultimately become Lagertha's murderer? Although most believe that Ivar the Boneless will fulfill his vow to take her life after she killed his mother Aslaug, there is a possibility that the former shieldmaiden will be assassinated by a different Lothbrok heir. Could Lagertha's alliance with Ubbe eventually lead to her doom?

King Ubbe Ragnarsson

In the midseason premiere of "Vikings" Season 4, Ragnar Lothbrok challenged his sons to kill him so they can take over as King of Kattegat. His eldest son with Aslaug received the most abuse from his father as Ragnar repeatedly slapped him and taunted him by calling him "King Ubbe." Although the tension was eased when Ragnar hugged Ubbe, there is still a possibility that Ubbe intends to rule Kattegat in the fifth season.

The "Vikings" Season 5 trailer that was revealed at San Diego Comic-Con confirms that Ubbe will take Lagertha's side in the upcoming civil war (via YouTube).

Once again, Ivar the Boneless declares that he will kill Aslaug's murderer but some believe that Lagertha's Assassin is much closer than she thinks.

How will Ubbe kill Lagertha?

There are speculations that the murder of Lagertha will resemble the scene where she took Hedeby back from a usurper. In the first half of "Vikings" Season 4, Lagertha killed Earl Kalf on the day of their wedding and declared herself Earl Ingstad.

Some believe that Ubbe will do the same thing to the current Queen of Kattegat, possibly murdering her right after they are married.

Will Lagertha die in 'Vikings' Season 5?

Katheryn Winnick may have already hinted at the possibility that Lagertha will not survive past the fifth season. During the show's SDCC panel, the star of "The Dark Tower" questioned creator Michael Hirst whether there will be a Season 6, as per Entertainment Weekly.

Some believe that Winnick had asked about the future of the series because her character may have been killed off in the upcoming season.

Will Ubbe murder Lagertha after their alliance is successful? Could Ivar the Boneless keep his promise and kill his mother's murderer? The truth will be revealed when "Vikings" Season 5 premieres on History on November 29.