Mercy is the third episode of the fourth season of Vikings. It is the thirty-second episode of the series overall. It first aired on March 3, 2016. It was written by creator Michael Hirst and directed by Ciarán Donnelly.
Ragnar and King Ecbert both experience separate visions of Athelstan, who relays the words "Mercy." Rollo attempts to learn the language of his new home, while enduring more of Gisla's mistreatment. Kalf hires a Berserker to assassinate Bjorn on King Horik's son's behalf. Erlendur gives the assasin a signet ring, which would allow the man passage for any who would stop him. Bjorn obsesses over killing a bear that has managed to escape his traps. Floki and Helga struggle to cope with the death of their daughter. Ragnar approaches the cave with an axe, tells Helga that she has suffered enough and frees Floki. Lagertha sleeps with Kalf and he tells her he loves her – however she fails to reciprocate. Aethelwulf has returned with the rescued Queen Kwenthrith and her son Magnus. Judith's obsession with Athelstan continues. Wessex continues preparing its soldiers, Count Odo readies a defense of Paris, and Ragnar cleans fish giving the impression that he is not ready to resume exploring distant lands.
- Travis Fimmel as King Ragnar
- Katheryn Winnick as Lagertha/Earl Ingstad
- Clive Standen as Duke Rollo
- Gustaf Skarsgård as Floki
- Alexander Ludwig as Bjorn
- Alyssa Sutherland as Queen Aslaug
- Ben Robson as Kalf
- Lothaire Bluteau as Emperor Charles
- Linus Roache as King Ecbert
- Amy Bailey as Queen Kwenthrith
- George Blagden as Athelstan
- Dianne Doan as Yidu
- Moe Dunford as Prince Aethelwulf
- Maude Hirst as Helga
- Owen Roe as Count Odo
- Edvin Endre as Erlendur
- Jennie Jacques as Princess Judith
- Seán T. Ó Meallaigh as Prudentius
- Nathan O'Toole as Young Bjorn
- Morgane Polanski as Princess Gisla
- Robban Follin as The Berserker
Additional Cast (in order of appearance)
- Huw Parmenter as Roland
- Karen Hassan as Therese
- Niall Cusack as Abbot Lupus
- Des Carney as Waerferth
- Stephen Rockett as Hvitserk
- Luke Shanahan as Ubbe
- Elijah O'Sullivan as Sigurd
- John Kavanagh, Peter Franzén, Jasper Pääkkönen, and Kevin Durand are not credited and do not appear in this episode.
- The Old French used in Vikings is almost not understandable for a French speaker today. Some words are no longer used, and others have changed since then. The letter s for example was used in words and with time has been changed by a letter with ^. Forest became Forêt. English kept the s in forest as in some French words likes forestier (meaning: "from the forest").
- In the Norse myth about Loki's punishment for killing Odin's favorite son Baldur, Loki's chains would break during the final days of Ragnarok, the Nordic version of the apocalypse. Upon which, he would head an army of the dead, seeking revenge against the other gods. Ragnarok would end with the death of the gods and their enemies, but also herald the return of the Christ-like figure of Baldur from the dead. This could be understood as a reference to Athelstan.
- Bjorn Ironside fights a bear, and in Norwegian and Danish, a bear is called a "bjørn." And in Swedish it's "björn."