well its not uncreative, knights are a top rank in the Hive line of command, it would make 0 sense to just come up with a new creature. I think the fact that crota is a knight is completely logical deduction from the hive architecture.
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I believe it would be like the knight at the end of the mission with the giant balls you shoot to finish it cant remember the name but you will know which i mean
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The one in the shrine of oryx mission? If so then I think its a good guess