280623
The herald demands Arthur swear immediate fealty to Matur , explaining that his country is defended by the contrivances of an inventor who has created a mobile palace carried by war elephants , invincible giants ( of whom he is one ) , and a mechanical dragon whose scream is so intolerable that it makes even the staunchest fighting men cover their ears , rendering them useless .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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