While not a fourth race, a Hybrid is a fusion of Lycan and Vampire at the cellular level. As such it is far more powerful than either species, with none of the weaknesses. The physical appearance of a Hybrid varies depending on the species it was first. A Hybrid with a Lycan dominant side resembles a Lycan in appearance. However, their faces are only slightly elongated, and their eyes are completely black. They also have little or no fur and blueish-grey skin. They also have talons like a Lycan, and the animalistic posture of a Lycan. Michael Corvin was the first of this kind of Hybrid to be seen. A Hybrid who was a Vampire first, on the other hand, has more physical attributes portraying its Vampire ancestry. While it shares the black eyes, grey skin, Lycan talons and musculature of a Lycan dominant Hybrid, a Vampire dominant Hybrid has noticeably bat-like ears flattened into its head, a bat-like nose, no hair at all and taloned wings. Marcus Corvinus was the first of this type of Hybrid to be seen.
A third hybrid type is implied in Underworld. Viktor's daughter Sonja fell in love with Lucian and became pregnant with his child. Viktor eventually discovered this, and feared the blending of the species that would result when the child was born. Viktor condemned Sonja, her unborn child, and Lucian to death. Sonja was burnt alive by sunlight. Viktor explains to Selene in the first movie that the unborn child was a betrayal of him and the coven, thus implying it would have both traits and an equal vampire and lycan features. However, there is no evidence on whether this type of hybrid would bear increased power or fewer weaknesses.
