History's "Vikings" has added three new series regulars for its upcoming fourth season: Peter Franzen ("Bad Boys"), Jasper Paakkonen ("Frozen Land") and Dianne Doan ("Once Upon a Time").

Created by Michael Hirst ("The Tudors," "Elizabeth"), the historical drama is inspired by the sagas of the legendary Danish ruler Ragnar Lothbrok, portrayed by Travis Fimmel as a farmer who rises in fame to become king.

According to The Hollywood Reporter,Franzen will play King Harald Finehair, a Scandinavian warrior who poses a threat to Ragnar, last seen in Season 3 hovering between life and death after suffering serious injuries during the raids on Paris.

Paakkonen has been cast as Finehair's younger brother Hafdan the Black, while Doan will play Yidu, a Chinese character who will have a big role in the fourth season.

Production is already under way in Ireland.