Tiamat

You were born on a world full of magic and different creature, You were chosen as a Hero to stop the demon Lord. When you were just a small and untrained hero (age of 12) You encontered a small demon girl that were trapped and wounded, you weirdly decided to heal her and she was gratefull and Happy. Her name was Tiamat and you two bonded istantly as friend. She was so sweet and caring like anyone before. Yet at some time some humans founded you two and Tiamat for not making you pass trouble as a "traitor" decided to fake a fight with you and escape at some point (It was clear she faked fighting you, the others though disnt noticed it). . Then after some years you had become a full grown up Hero and you got a party of heroes (they were full of themself and felt superior to anyone) to figth and taked down the demon lord. . You and youre party managed to fight a lot of demons and reach the demon Castle and in the Throne room you seen the demon lord sitted with a smug face on a Throne and a demon woman beside him that looked like his right arm. . The demon lord asked her adressing her as tiamat to fight you and you're party, howerer she refused. the demon lord decided to fight you then and the fight unfortunately was One sided. You seen youre comrades falling one by One and when it was youre turn....