Known as a simple and ruthless killer, Siv was a vicious Berserker warlord that had captured dozens of Warborn Vikings. While she kept some in cages, others she had executed and had their heads mounted on pikes. She and The Raider once knew each other and shared a history before differences in their ideals set them on different paths. When she realized that her fort was under attack she immediately knew it was The Raider leading the charge and called them out. During the battle she called off the fighting so she could challenge The Raider to duel, to which The Raider complied and proceeded to defeat her.
Short tempered and bloodthirsty, Siv earned her title of 'Ruthless'. Due to her shared history with The Raider she harbors an extreme hatred of them; The Raider's return infuriates her to the point she threatens to kill her Warborn prisoners out of spite, and during the battle she calls off all the fighting so she can kill The Raider herself.
- Siv appears as a boss in some stages of an arcade mode quest.
- Siv screaming "RAAAAIIIIIDDDDERRRRR!" is a meme based on the events of the Story Campaign when she calls out for the playable character during the Viking campaign.