Okay, i know that every one gives shit to destiny for supposedly having the last boss of the game "3 of the same minibosses" but i dont think its quite true. i find it really interesting actually. just take a look at them for a second. the Sol progeny arent just three gate lords. in the final level you essentiallly fight the past, present, and future vex all in one X point in space. just take a look at the sol progeny.(Grimore) and look at them. one of them (in the middle) looks as he belongs to the line of the precursors. the precursors (grimore) states "Awestruck Ghosts report encounters with ancient Vex, their casings built long before the age of humanity. It would be easy to assume these Vex are the ancestors of those we face today - but with the Vex it is never so simple. " that means that the middle sol progeny is from the past. now look at the one to the left. his head shape puts him in the line of the Decendants.(Grimore) the decendants are the vex from the future. the grimore states "Survivors of the Vault of Glass report sightings of ancient Vex - ancient in the sense that they have endured for eons. Convergent analysis from multiple Ghosts suggests that these Vex exist in our future. and lastly, the sol progeny to the right resembles the vex in our present. so seeing as how the black garden is a place closed off to time and space. it is a place where the vex from all the time periods meet like and x,y, and z. maybe in the black garden the vex from the past, present, and future sent their own guardians to protect the black heart. and when you enter the black garden, you fight the vex from the past, present and future all in one moment, in an area closed off in time. what do you think? comment below.