There is a magical ward rune that works against vampirism. Even lava dragons start to use vampirism; this has been verified in a duel. You can kill a Dwarf early on due to its slow start, or in the middle of the game because Dwarves usually have trouble with logistics. Also, the Dwarf's skill progression can go wrong: it might want to focus on Haven, but it will keep getting Chaos skills.
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