Alright, so looking at the thoughts of meh brony and brass beau if Grogar being real: (
@Meh brony
@Background Pony #1847
He more than likely would’ve been the true final villain of season 9 and by extension the tv series as a whole.
Grogar would have reversed the flow of magic (it is his bell) and drained the trio. 50/50 odds on redemption, 70/30 on reformation.
Given that they wouldn’t have had grogar’s magic to make them as big of a threat what I believe what would’ve happened is in in worst case scenario that all three of them would’ve been sent to Tartarus instead of being turned into a statue, a second plausible best case scenario is that the three of them would’ve experienced an even evil has standards moment under grogar and potentially helped the heroes defeat him, which in turn would convince the ponies to give them a second chance albeit under very tight scrutiny, not unlike how the mane six initially treated discord during the early stages of his reformation.
)
I can’t help but also imagine discord either being tied up by grogar, or arriving late and noticing the drained trio.
I can also assume that grogar ends up being the one in stone.
As for the trio, I feel another option for them would be being banished from equestria (Yes, I know, harsh, but they’re the villains, so…).
Or, taking meh brony’s thought (“the three of them would’ve experienced an even evil has standards moment under grogar and potentially helped the heroes defeat him, which in turn would convince the ponies to give them a second chance albeit under very tight scrutiny, not unlike how the mane six initially treated discord during the early stages of his reformation.”), have it reveal that he wants to kill centaurs and changelings (we don’t know if he actually would act like that, so I had to imagine he would). That would be what would convince the three of them to realize that standard. Next to the fact that he would severely injure celestia and thorax (possibly shocking the three).
Honestly, I think it’s definitely up to debate on how it could go.