History HD has begun releasing teasers and an official full-length trailer for the upcoming "Vikings" season 4. Most of the footage focuses on the upcoming battle between Ragnar (Travis Fimmel) and his brother Rollo (Clive Standen) but as stated by the IB Times, the teasers also hint at Ragnar's impending death.

One scenery that appears in the teasers is the theme of snakes. There is also a quick shot of Ragnar being tied in a cave as well as King Aelle (Ivan Kaye) stating that he'd willingly sell his soul to the devil in order to achieve his Earthly goals which fans recognize is to kill Ragnar. Their conflict began as early as season 1 when Ragnar invaded Aella's lands.

The recurring image of a snake, as explained in the report, is important because in the original mythological story Ragnar dies when King Aelle tosses him into a pit of snakes. However, it is because of this act that Ragnar's sons invade Britain and wage a war to exact vengeance.

As previously reported, there is also the fact that actor Travis Fimmel is possibly leaving the show in order to focus primarily on his new movie career now that he is starring in a potentially big film franchise, starting with this year's "Warcraft" movie. If this proves true then his sons will take centerstage as the main characters of the series.

Many scenes in the trailer and teasers also focus on Bjorn (Alexander Ludwig) rallying the people in his father's name, indicating that after Ragnar's death the responsibilities as king will pass down to him. One of the shorter teasers also showcase Bjorn using his authority to arrest Floki (Gustaf Skarsgard) for the murder of Athelstan (George Blagden).

Before any of these conflicts will take place, however, Ragnar will still need to deal with Roll,o who invades Kattegat despite the emperor of France advising him not to.

"Vikings" season 4 is set to premiere this Feb. 18.