When you return to the Crucible ten years later (after the Tattered Spire), it is best to have some five star skills. Included in these skills should be Slow Time and Chaos. You should also have a five star Fireball attack so that you can wipe out most enemies around you through most of the rounds and get Perfect Rounds. When you get to the eighth and final round against the Rock Troll, wait for the Spores to appear then dodge the rocks and cast five star Slow Time. Run up to the troll, cast five star Chaos, then take out your fastest and most powerful ranged gun. Shoot the Spores until they are all gone before Chaos wears off. Alternately, cast a five star Lightning or Fire attack (non-enemy targeting) and hope that it will destroy all the Spores instantly. Otherwise, repeat the process until the Troll is dead in under one minute fifty seconds.