Birna Bran is the main antagonist of Skellige arc in The Witcher 3: Wild Hunt.
Birna Bran was a wife of King Bran Tuirseach and the mother of his firstborn son, Svanrige. After the death of her husband, she refused to give up power and began to style herself "Queen Mother" in hopes that her son would become the next king.
When Geralt of Rivia arrived in Ard Skellig to meet up with Yennefer, King Bran had passed away and Birna Bran was among the many to attend his funeral. However, instead of following Skellige tradition where she was expected to let herself die on her husband's pyre as it was set out to sea, she stayed behind and one of Bran's younger concubines took Birna's place instead.
Later, during the wake, Birna discussed with Yennefer her distaste over Skellige's tradition of electing a king rather than it being hereditary like the Continent monarchies and, naturally, wanting her son to become the next king. When all the possible candidates put themselves forward, including Crach an Craite's two children, she tried to convince the jarl of an Craite to tell his children to back out but he refused.
Deciding she had no other option, Birna schemed to remove all the other throne candidates by enlisting Arnvald's help in spiking the feast's drinks with a mixture of blood and mushrooms and then sent her son away from the main hall. When the spiked mixture was drunk, berserkers at the party transformed and began to mindlessly kill everyone around them, including almost all the candidates in the hall except for Cerys and Hjalmar. However, because the incident happened at the an Craite stronghold, the clan was blamed for the incident and if they couldn't figure out the truth, the throne would automatically go to Svanrige.
If Geralt chooses to help Cerys: Eventually, Birna's involvement was discovered but when the issue was brought before the jarls, Birna smoothly denied their accusations. However, Svanrige realized she sent him out of the hall before the attack and asked the jarls if they would give credence to a man who turned on his own mother. This caused Birna to inadvertently admit her guilt, prompting the jarls to sentence her to death. Birna was then chained to a rock on a small isle north of Sund and left to die.
If Geralt chooses to help Hjalmar: Geralt and Hjalmar then went to Fornhala, which seemed abandoned at first until they found a bloody corpse near an altar to an outlawed deity. Geralt then used his Witcher senses to figure out what happened, leading him to a cave.
Inside the cave, he and Hjalmar witnessed a ritual conducted by a druid which transformed normal men into berserkers, granting them the ability to transform into bears. When the ritual was finished the two confronted the druid, who explained the vildkaarls willingly executed the massacre at the feast so that they could support their king but refused to name him and a fight breaks out. After defeating the druid Geralt found a letter on his corpse, unsigned but confirming Geralts suspicions that the vildkaarls were only working for someone.
If Geralt doesn't help Cerys or Hjalmar: Birna negotiated without the jarls' consent to pledge Skellige to Nilfgaard and continued to speak for Svanrige despite him being named king. The diplomat from the Empire then asked for the new Skellige king to say the pledge himself, and Birna turned to her son. However, Svanrige killed the diplomat, shocking Birna and uniting the jarls in their fight against Nilfgaard.
Journal entry Edit
It can be difficult for a woman to gain the esteem of knights and warriors not accustomed to seeing female hands on the reins of power. It helps little when, like Birna, widow of King Bran of Skellige, the woman seeing power is filled with acrid disdain for her countrymen and their customs. One might argue that disdain is a valid reaction when, in the case of the passing of a man of power who embodies tradition, those customs call on her to follow along since outdated ritual and cast herself upon her husband's funeral pyre.
Justified or not, Birna's desire to rewrite age-old Skellige traditions put her at odds with the jarls and made it unlikely she would be remembered alongside Calanthe of Cintra or Meve of Lyria as a successful and revered ruler.
Birna likewise refused to hide her disgust with the custom of choosing a ruler by vote of the jarls. She dreamed of establishing a hereditary kingship in Skellige and thought the ideal dynasty to hold it was her own, starting with her and Bran's son, the young Svanrige.
In all probability it was this longing for power that drove Birna to concoct the conspiracy that ended in the massacre at Kaer Trolde.
The evidence gathered by Geralt and Cerys sealed Birna's fate.