I was thinking, even though I knew it was impossible.
In the fourth season of Legacies, they could bring in a powerful villain like Dahlia or the ancestors. Yes, I know it is impossible because Dahlia is dead and has found peace (and she cannot resuscitate anyone who finds peace) and the Ancestors are now free. But let's pretend it was possible to bring them back.
The Ancestors would be an excellent villain because they had enough power to destroy more than one entire city, in addition, they were powerful enough to corrupt an original vampire and create the Beast without channeling any celestial event as Esther did or as Qetsiyah did.
Dahlia would be a good villain for being the firstborn and being extremely powerful, as well as being the only one capable of giving the training that Hope needs. It almost destroyed an entire city, which means that it will not be an easy element to fight.
Why would they be good villains?
Well, we could see the powers of Hope, Lizzie and Josie being fully explored, and it would explain the ancestral and ancestral magic of Dahlia and Esther's lineage. I think it would be a good one, especially that a large part of the fandom is complaining about this script and would bring something more "scary" and challenging - in addition, they could use Dahlia to explore the ripper side of MG.