For the maybe-defunct vampire book I was working on with someone a couple years ago, the Upier is described in mythology as a "hideously ugly" vampire with a harelip and a stinger-like tongue.
I went all the way and made the whole thing a warped mutant, with its face sort of "caving in" to make way for the tongue.
The Upier is also said to sleep in a basin of human blood, and when killed, erupts into maggots, rats, snakes and insects. If even one escapes, the Upier will return for revenge!