A Blood Mirror holds the power of a Vampire clan.
The Dracula Blood Mirror first appears in the episode "Mirror Mirror". Vlad and Boris, with a little help from Eric Van Helsing, read about it's existence in A Painless Cure for Vampires. They enter the crypt, where they overcome the castle's defences and enter the room where the artefact is stored. Ingrid is seen smashing a large mirror. The real mirror is much larger and more impressive.
The mirror appears briefly in "Bad Reflection" when Boris changes into a vampire. It's power is not shown.
In "Sweet Sixteen" Ingrid approaches the mirror for her transformation. Inside the mirror, the vampiric reflection shows Ingrid her 'future'. Suddenly the reflection tears at the glass and Ingrid runs away in fright. The evil reflection is able to free itself and it follows Ingrid all the way to school. Eventually Ingrid and the mysterious entity merge and she becomes a fully fledged vampire.
In "Bad to the Bones" mysterious voices lure Vlad to the Blood Mirror. The guard creatures hurl him in, trapping him in the world beyond. Inside the mirror Vlad encounters not just one evil reflection, but a thousand.
After merging with them, Vlad becomes cruel and wreaks havoc around Garside Grange School. Eventually he is able to separate himself from his reflection. They merge fully back in the mirror room.
In "Kiss of Death" Vlad orders the guards to open the mirror vortex. The world beyond has changed dramatically since series 3. Vlad states that he controls that side, so the wooded lake and the throne may have been his creation (or it might be part of the Dreamworld). Elizabetta and Malik are also under his control and he is able to 'zone' Elizabetta and throw her into the lake.
- If it's smashed, every vampire in that clan would supposedly turn into its mortal state (which would result in death for old vampires)