Sebastian can be described as snarky, unpredictable, swift and violent at times. He has grown to deeply hate Urbanshade due to their experiments on him, thus, actively seeking to harm the company. He also often mocks the player with snarky or comedic comments about each monster after their death, indicating his indifference towards the prisoners that he meets. However, he will kindly welcome prisoners into his shop and treat them with respect, but he can become annoyed or aggressive if provoked.