Ok this is a crazy theory but what if the heart of the black garden was one of the nine
If I remember correctly it’s been kinda establishing that the bin are primordial planetary intelligences almost like ego form guardians of the galaxy 2, what if the heart of the black garden was the planetary intelligence of mars.
It doesn’t make sense to be the darkness since it didn’t attack us and was being worshipped something the darkness doesn’t seem to care about
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<It is not one of the Nine, otherwise we'd only have 8 Nine and all of them are clearly talking to us. You seem to misunderstand that the Black Garden isn't ON Mars. It never was until we destroyed the Heart. The Black Garden is a place outside of time and space, created by something nobody understands and tended to by the Vex because instead of ruining them, the Garden IMPROVES them. The Heart is not the Darkness itself, but it's possible, even likely, to be a thing left behind. Uldren Sov theorizes that it was bait, something to tell its masters how strong the Traveler's getting. If he's right then we're -blam!-ed^2.>