Not all vampires in the land of the dead are bloodthirsty killers that want to take over the world. Some are satisfied with immortality and want to spend an eternity without strife in seclusion away from contant war with the humans.
"Many strange things may be seen in the Great Swamps, not all real. But I tell you, there was a ship and it was real! Well it was old and all sails torn and had many holes in the hull... but anyway it was hundreds of miles from the Sea! How it came to be there, I can only wonder..."
(If it is not a hallucination, may be inhabited by wererats.)