It's totally official I was browsing through my grimoire and read one of the first ones about the black garden and I'm now under the assumption that the traveller is evil |:. A guy dies in the shores of time, ends up in the black garden, he finds a ghost shaped flower. He goes to pluck the flower and gets cut aaaaaannnnnnddd no spoilers after that (:
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The black garden is inside the Traveler.