MarkB
Legend
This is one I posted recently in another thread, but it seems appropriate here.
Mordenkainen's Vampiric Mansion
Through an odd set of circumstances, an unfortunate wizard-turned-prospective-vampire-spawn was once buried within an interior garden feature inside his own Mordenkainen's Magnificent Mansion. The mystical connection between a vampire and their place of burial played havoc with the normal spell-duration restrictions of the Mansion, and when the spell ended the Mansion and its newly-vampiric occupant were cast adrift in the Astral Sea, bound together and doomed to slow decay.
The vampire, himself a formidable wizard in life, began to devise specialised ways for his abode to leech power from other extradimensional spaces, and for himself to feed. It started small - sometimes when a person reached into their Bag of Holding they would find their arm grasped in powerful hands as fangs fastened to their wrist. When their drained corpse was found, its hand would still be thrust into what was now a perfectly ordinary and otherwise-empty sack.
Now, after hundreds of years, he's perfected his craft, and when a group of weary adventurers retreat to the safety of their lavishly-appointed mansion, they may find that it has more and different rooms than they remember, as the Vampiric Mansion has locked onto it parasitically.
I imagine this as the ultimate high-level haunted house adventure. A party already weakened from a day's activities finds themselves locked inside their own mansion, its dimensions warping in unexpected ways under external control as a smart and deadly killer stalks its halls. To win free they'll have to fight their way from their own mansion into the heart of the vampiric mansion that's become bound to it, all the while fighting the architecture itself, as the vampire has become inextricably bound up to the house itself, becoming almost more a living location than an individual creature. A major aspect of the adventure would be a battle of wills between the party's spellcaster and the vampire, as each of them attempt to exert control over the shape of the mansion.
Mordenkainen's Vampiric Mansion
Through an odd set of circumstances, an unfortunate wizard-turned-prospective-vampire-spawn was once buried within an interior garden feature inside his own Mordenkainen's Magnificent Mansion. The mystical connection between a vampire and their place of burial played havoc with the normal spell-duration restrictions of the Mansion, and when the spell ended the Mansion and its newly-vampiric occupant were cast adrift in the Astral Sea, bound together and doomed to slow decay.
The vampire, himself a formidable wizard in life, began to devise specialised ways for his abode to leech power from other extradimensional spaces, and for himself to feed. It started small - sometimes when a person reached into their Bag of Holding they would find their arm grasped in powerful hands as fangs fastened to their wrist. When their drained corpse was found, its hand would still be thrust into what was now a perfectly ordinary and otherwise-empty sack.
Now, after hundreds of years, he's perfected his craft, and when a group of weary adventurers retreat to the safety of their lavishly-appointed mansion, they may find that it has more and different rooms than they remember, as the Vampiric Mansion has locked onto it parasitically.
I imagine this as the ultimate high-level haunted house adventure. A party already weakened from a day's activities finds themselves locked inside their own mansion, its dimensions warping in unexpected ways under external control as a smart and deadly killer stalks its halls. To win free they'll have to fight their way from their own mansion into the heart of the vampiric mansion that's become bound to it, all the while fighting the architecture itself, as the vampire has become inextricably bound up to the house itself, becoming almost more a living location than an individual creature. A major aspect of the adventure would be a battle of wills between the party's spellcaster and the vampire, as each of them attempt to exert control over the shape of the mansion.