His name is Lucian (played by Michael Sheen).
Lucian is the Lycan clan leader in a war against the Vampires.
He was instrumental in the tracking of rogue Lycans. Lucian later helped defend the vampires in the castle he served in against angry humans, by driving them off with vampire bats the attackers believed to be actual vampires.
The Underworld series is four films deep and continues to plug along successfully, with Underworld: Blood Wars coming out January 6, 2017. Here are 10 random thoughts about 'Underworld' shared by Moviepilot.com.