Beryl has heard that the love between Serenity and Endymion is destined. They are star-crossed lovers torn apart too soon. Love that destroyed them; love reunited them. That, and destiny.
Beryl does not believe in destiny. She believes in opportunity. She believes in taking, possessing, and keeping.
That is why she does not feel guilty when she takes Endymion to bed, and stares into his empty eyes as he fucks her into oblivion. All that matters is that she has him.
Beryl hates the word destiny almost as much as knowing she cannot have Endymion forever. It isn’t her destiny.