Originally Posted by
Sergard
Talia should be the obvious guess (not Jason; thank you, Damian)
But it doesn't add up with the story in "DC's Year of the Villain Special (2019-) #1". Leviathan calls Batgirl "Barbara". I don't think that's something Talia would do.
On the other hand, Jason wouldn't wear a strange mask and a cape. He even stated in the TT Annual that he doesn't like capes. But seeing how Damian behaves in the Special compared to his falling-out with Jason in TT, it doesn't look like Bendis actually read the annual.