Caim is a skilled warrior that is the pact-partner of the red dragon Angelus. His pact sign is located on his tongue signifying that the price of the pact was his voice. His hallmarks include his unique sword and later his missing eye.
Caim has a deep-seated hatred for the Empire following the death of his parents at the feet of an imperial dragon. As a warrior of the Union, Caim protects his sister from the Empire's machinations. Furiae, his sister, is the goddess and a seal against the apocalypse.
Caim is mortally wounded in battle outside the castle housing his sister. He makes his way to the castle's courtyard where he encounters a red dragon that has been captured by the Empire and is near death herself. There Caim makes the decision to put aside his resentment of dragons and form a pact with her. The dragon grudgingly accepts his offer and their fates become intertwined. Caim loses his ability to speak because of the pact, but both he and the dragon are spared from death.
Caim and the dragon set out to fight against the Empire with their new-found strength. Unfortunately, always one step behind, Caim and the dragon cannot stop the Empire as they destroy the seals that keep the world from descending into chaos. Inuart who was once a friend is lured to the Empire's side by his desire for power to protect Furiae. After he makes a pact with a black imperial dragon, he defeats Caim and takes Furiae to the leader of the Empire named Manah. Although Manah is just a child she has become possessed by the gods. The gods then partially possessed Furiae and she kills herself, bringing on the end of the world. Caim and the dragon manage to defeat Manah. The dragon decides that she will become the Guardian of the Seal even though she despised humans before she met Caim. She reveals to Caim her true name is Angelus and then disappears as Verdelet finishes the ritual making her into the goddess. (Canon storyline)
Caim takes Manah across the world so that she may witness the suffering that she has caused. Meanwhile, Hierarch Verdelet creates the Knights of the Seal to protect the seals. During their travels Caim feels Angelus' pain as Verdelet increases the load of the seal upon her, Manah takes advantage of this and stabs Caim in the eye and escapes. Furious, Caim finds and kills Verdelet for what he has done. He then sets out to destroy the seals that keep Angelus bound. During such an attack on the District of Shining Life, he mortally wounds Urick and kills Nowe's adoptive father, General Oror.
Eighteen years have passed since the events of the first Drakengard and at age forty-two Caim has come to be known as the one-eyed man, a dangerous renegade. He encounters Nowe's party and he attempts to capture Manah, but with the help of Urick they escape. Later he catches up to them at the District of Shining Life where Urick is the guardian. Although Nowe's party is attempting to break the seals as well; Nowe still attempts to defend his friend Urick, but ultimately Urick sacrifices himself to save Nowe from Caim. Urick's body is immortal from his pact with the Reaper, but the Reaper itself is killed by Caim thus ending Urick as well. With his last breath, Urick manages to push Caim into a chasm where he is presumed dead.
Once the last seal is destroyed Angelus is freed. Driven mad by the burden of being Guardian of the Seals, she burns everything in her path. Caim asks for Nowe and Legna to kill Angelus and end her suffering. The two manage to find her and defeat her and she falls below to Castle of the Goddess, where her pact with Caim began. Caim appears and comforts Angelus as fire swallows her. Caim smiles gratefully at Nowe as he too turns to ash.