When we are accessing the area to face the boss Vladrukh, we notice something different about the surroundings: there is a sealed door with a coffin just behind it.
As additional information, this door is close to one of the tasks in the Bloody Tusks quest, where the objective is to protect Anaztassja Moroia from attacks by different types of Norcferatus while she performs a kind of ritual. A few square meters away from the door is a ritual scroll, which when used transforms the player into a bat or rat (at least that's what we've seen so far).
But regardless of whether you have defeated the boss Vladrukh or clicked on this scroll daily, the result is the same: the door does not open.
So the following question arises: What should I do to open this sealed door? Is there something related to the ritual scroll near it? Are the items called Tiny Bat Coffin and Special Bat Coffin related to this mystery?