Hair can't be cut with normal razors

Wester washed in a basin of water and studied his beard in the mirror
above it. Shaving was a complicated business for vampires. Normal razors
were useless on their tough hair. He and Larten had picked up specially
hardened blades a couple of years ago, but Wester had lost his in the course
of their travels. He’d asked to borrow Larten’s, but the slightly older
vampire had said it was time Wester learned to take better care of his
possessions. Larten had just been teasing him, but Wester didn’t want to
give his friend the satisfaction of seeing him plead, so he’d grown a beard
since then.

***

The Saga of Larten Crepsley: Ocean of Blood, Chapter 1