Dead Elixir

My game is called (Dead Elixir). This game is about a kingdom, this kingdom controlled by a kind king and irresponsible son and courage hero. One day the celebration of a new king has been chosen and everyone has been celebrating happily then the main event begin when everyone has to drink from an elixir for the new king. But for a second the celebration become chaos and everyone run in every side and one of the citizen said "Help me!! help zombie! it is a zombie" so the king realize that there is something awful happened. he said"everyone relax please it is just a one zombie we can defeated it!" but the worst scenario has become! all the citizens that have been beaten become vampire zombie!. a zombie who can survive more than normal zombie and can kill most of their victims by drinking their blood and become zombies!. So, who can defeat those monsters? and how can you know the secret of this Elixir!