The Ending Choices in Blood and Wine DLC
The only way to finish it is to kill the beast (Dettlaff). Both sisters will also die no matter whether you will go for the conversation with Syanna.
Impact of Romancing Syanna
Romancing Syanna has no impact on the rest of the game and the other romance options that Geralt can pursue.
Regis: The Higher Vampire
Emiel Regis Rohellec Terzieff-Godefroy, or simply Regis, was a very powerful higher vampire, and more than four hundred years old when he first met Geralt of Rivia. He was the barber-surgeon of Dillingen but surprisingly intellectual for one in such a profession.
Revealing the Truth About Syanna and Rhena
Approach the manor and another cutscene starts where you see the truth for yourself: Rhena and Syanna are one and the same person.
Fighting Orianna in the Game
Oriana main strength is to poke you down, dodging her abilities will make it hard for her to win Lane against you. Another way of beating Orianna is roaming. Orianna does not have the greatest time at roaming so if you can out roam her and help other lanes then it will be very good for not only you but your team.