Doru

The shape is Doru, a vampire spawn sent by Strahd to torment Donavich and cast down the church. Doru is starved for blood and brave enough to attack a lone character. If the characters approach as a group, he does his best to avoid them while hissing, "I can smell your blood!" If they cut off his escape, he lunges forth and attacks.
If the characters restrain Doru and either promise him blood or threaten to destroy him, or if they kill him and then raise him from the dead, he recounts the events that led to his downfall (see area E5f).