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Set in a fictional universe, often (but not always) with fantastic or supernatural elements, alternate worlds, magic and monsters.

Science-fiction. Commonly including things like aliens, advanced technology, and settings of outer space or distant planets. 

Shambling undead humans who died after being infected by some sort of virus and are now "alive" again, commonly known for the desire to kill living human beings. Commonly paired with the (post-)apocalyptic genre.