As far as I know, no one knows. I don't think it's confirmed anywhere. This is from the Sol Divisive Grimoire Card: Legends and scant field reports all indicate that the Divisive Vex behave religiously. Why would a hyperintelligent, time-spanning thought mesh exhibit religious behavior? The answer seems as obvious as it is chilling: if the Vex found worship and devotion more effective than any other behavior, they would adopt worship. Whatever the Vex found - or made - in the Garden, it transcends even their power. It seems very likely that they discovered (as in did not create) [i]A[/i] power led them to worship and the Black Garden would certainly be related to it, but the Black Garden--even the Heart of the Black Garden--and that power are not necessarily one and the same so the Vex could have created the Black Garden, including the Heart, or maybe not.

Sol Progeny Grimoire Card: The Vex, for all their voracious intelligence, could not understand or decipher what they found.

That's a good find. I'd say that makes it likely that the Heart at least was found. It might be safe to assume that and I totally understand that I'm probably just being argumentative, but this is how I think things through and it's fun, so BUT Ikora does call it a hypothesis, and while she said, "the Vex saw the abominable presence at the heart of the Garden as a divine power," unless she has other information she hasn't shared with us, that has to be based on our own report of what we observed and we don't know the exact nature of the relationship between the Vex and the Heart. Does she know that the power the Vex were worshiping was itself present? Or could the Heart have been a doorway the Vex built through which they could worship this power and this power could apparently create agents of its will (doorway also possibly being a loose term here, like what if they created that goo knowing that this great power could act on/through it)? And if the Heart was part of the power they discovered (again, it's probably safe to assume they discovered this power but it isn't impossible that they created it themselves), how did it get there? Did the Vex put it there, or help it get there, or did it do it on its own? Ikora says, "We must assume the abomination was part of something greater," so I would think it came from somewhere else and we don't know how it wound up in the Black Garden. I've never really understood what the Darkness is and playing through the game I thought the Heart was part of it. So I believe the Heart was part of the Darkness that they found and built the Black Garden around and prepared three servants to be used by the Darkness (which I just realized would probably mean they had to be able to communicate with it). So I agree with you, but what I'm saying is we don't KNOW know, you know?

But if they couldn't understand it or decipher it, it's really hard for me to believe they could find a way to contain it and build an environment around it. What I could see is that they found the garden and the heart as is and built their own structures around it, just like they tried to do in Oryx's throne world when Crota accidentally let them in. Even if their structures are what locked it out of time, maybe that's part is the structures' purpose, but I'm convinced the garden itself was found.

That's a very good point. And I agree with you and Ikora. Everything I am talking about is if she is wrong, and I'm saying that it's unlikely but possible that that's the case. The logical conclusion is that the Vex found a power greater than themselves that they can't understand, have discovered that worshiping it helps them in some way, and that this power is the Heart of the Black Garden. If that's all true then it seems very unlikely that they would be able to build stuff relating to or interacting with this power. Except that it seems that they built three giant Vex that do exactly that. Since they're worshiping the power and possibly working together I don't think they would need to contain it but I agree that they wouldn't be able to. The garden part of the Black Garden--I have no idea. Neither the Vex, the Heart, or the Darkness (if that's what the Heart is) seem like the gardening type to me.

I don't think they really had to do anything special, though, to have those Vex possessed by the heart. The card says it can make others do its bidding at will, just like the Traveler does with the guardians. We were chosen, not made. It seems like we are what's available to the Traveler, just as the Progeny were what's available to the heart.