Warren is a relatively tall middle-aged man with long black hair and glasses. He also frequently dresses in dark clothing, with deep side pockets, where he often places his weapons. Warren also has a large droopy mustache that makes him somewhat resemble a walrus.
Warren was born in the town of Khalek, a village recuperating from horrendous raids from early in The Great War. Due to these circumstances, Warren developed a knack for helping others as well as an outer toughness. From a young age, Warren's father would tell him tales of "evil" demons, of which he described as "horrific beasts" who would destroy everything in sight. This began his lifelong fascination with demons, so much that he eventually decided to become a demon hunter. He killed a great many demons during his time as a hunter, and even declined an offer to become mayor of Khalek in order to keep hunting the demons. However, a disaster soon struck when Warren was 30 years old. The disaster involved some rogue tricky demons implanting a bomb in Khalek, leading to the destruction of the town, as well as killing his father in the process. Feeling guilty that he had let the demon hunting go to his head, Warren cut all ties with his family and moved to Silivia for a new start. This new start involved being nice to every human he saw, as Warren felt it would better suit him in his master plan to avenge Khalek.
Warren is shown to be quite caring and considerate as when he sees Savannah passing out, he tries to help her and even offers her to stay at his place. However, he is known to be quite vile to beings he considered as evil.
Warren is well-trained in combat. He also has incredibly strong senses of touching, tasting, hearing, seeing, and smelling. He is also gifted with an eidetic memory, which makes it easy for him to write books. As a result of his time hunting demons, his instincts are higher than the average person.
- Warren actually has first-hand knowledge of how Silivia's silver lights work, having fought a pair of unruly demons underground once. During the fight, he crashed into one of the crystals and accidentally caused a power outage in the metropolitan area of Silvia.
- Warren's experiences have inspired him to write a great many novels, which recur throughout the series and are known for their graphic realism.