You do specify Sailor Moon Crystal (which I know nothing about beyond what I can guess from the name) as the version Garrick will be interacting with, but any chance of the old anime's Doom Tree material making an appearance? Given that the whole problem for that plot was resolved when the ailien twins (and that typo just made me realize, they were named "Ail y Ann." Groan.) figured out they were feeding their giant space tree the wrong kind of emotional energy, Garrick should be able to set them straight right off.
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‎noli esse culus
‎noli esse culus