I think Crota will look similar to "Sardok, Eye of Oryx", but with a Hive boomer & his sword.
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He's gonna be a giant snake that shoots knights from a gravity cannon, he will one shot you from the beginning of the hellmouth. He will also auto expunge when his health reaches 10% so at 11% you must stop and perform dance moves in sequence to take his remaining health, 1% per hour