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Magnus of Livonia besieged the town in August 1577 , but was deposed and replaced by Russian forces under tsar Ivan IV who eventually sacked the town and castle in what became a symbolic victory .
 Magnus of Livonia, Ivan IV
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Magnus of Livonia, Ivan IV