A castle was generally a fortified house owned by kings and queens
There are different reasons as to why castles became palatial. One main reason is because castles were no longer needed for defense, therefore were turned into palatial castles where people were free to visit and stay in.
the door and the walls protect the people inside
Only some vampires own castles, it might be for different reasons, like they are "vampire royalty" or they just plainly want to stay out of people's way.
A castles main defense were it's high stone walls and sometimes a mote, a channel of water
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members of the Baronage had there own private castles and the Royal households of countries also owned some
Palaces are used for Kings, queens, princesses and prince's and castles are used for safety
William the Conqueror built the first wooden ones but kings after him also built their own castles.
Castles were expensive to build, they were expensive to equip, their garrisons were expensive, and they fell apart of their own accord if they were not maintained at some expense. Once cannons were made useful and widespread, castles had lost a lot of their appeal.
Most castles were built in the 16 hundreds.
Because they needed a more better place to fight because wooded castles could catch alight in war a stone castle would not also they needed a more main sturdy home.
Because in historic times India was divided into various states and every state used to have their own king. All those kings have their own reigns and they used to live in their own castles.