One vamp can always recognise another

There were dozens of ice sculptures dotted around the cavern and
hanging by ropes from the ceiling. Some of the sculptures were of objects
— a chandelier that looked like it was decorated with candles, a drinking
fountain, a four-poster bed, several chairs and thrones. Others were of men,
or to be more precise, vampires. Even if there hadn’t been the marks on
their fingertips and the scars of warfare on their faces and limbs, Larten
would have known. One vampire always recognised another, even if that
other was only an icen statue.

***

The Saga of Larten Crepsley: Palace of the Damned, Chapter 2