Angelus is a red dragon that has lived for over ten thousand years. She had seen much on the actions of humans and has been spiteful toward many of them, for their wrong-doings towards each other and toward other dragons.
She was hunted down and captured alive by the Union Army, where a swordsman and soldier of the Union had found her--named Caim. Memories of Caim's parents being eaten by one of the Imperial's black dragons flooded his mind. Enraged, he lifted his sword and was about to kill Angelus in revenge until he realized that he too was wounded. Caim then asked Angelus if she wanted to live.
In desperation, he offered Angelus to make a pact with him. As Angelus laid there, suffering, she asked Caim why he thought he was worthy of making a pact with her. "Worthy or not, I wish to live," he told her. In seeing that the dragon was still hesitant, he demanded an answer; a pact, or death.
Soon, enemy soldiers ran into the room, and Caim rushed into battle to slay the entire group. Angelus watched as he survived them all, and in awe she said that he had the devil's luck. Eventually, the need to survive overcame her pride and the two who had the one thing in common--the need to live--formed a pact.
Soon after they fended off more enemy troops from reaching Caim's sister Furiae, the goddess who bore a seal to protect and help keep the peace within the world of Drakengard...they both discovered that the sacrifice that was made to seal their pact was the loss of Caim's voice.
When it was too dangerous to protect the goddess in the same place and had to move her to a safer location, their quest (with allies and their pact partners they made along the way) to put an end to the evil the Empire and Cult of the Watchers started once and for all...
[[RP account for non-profit entertainment uses. Angelus here I'm taking from the middle of the first game's storyline. :)]]