I agree that Death seems the most likely candidate, I find it very interesting how Triss' attempt to identify/locate Death was described: her spell pierced one magical barrier, and then another, but after that there was another and another ad infinitum. So I guess Death dwells on a plane unreachably far away.
"The darkness thickened. Ciri saw yet another great door in front of her. Yennefer did not slow her stride but Ciri suddenly knew that this door would not open of its own accord. And she suddenly had an overwhelming certainty that this door must not be opened. That she must not go through it. That, behind this door, something was waiting for her . . .
She stopped short, tried to pull away, but Yennefer's hand was strong and unyielding and unrelentingly dragged her forward. And Ciri finally understood that she had been betrayed, deceived, sold out. That, ever since the first meeting, from the very beginning, from the first day, she had been no more than a marionette, a puppet on a string. She tugged harder, tore herself away from that grip. The darkness undulated like smoke and the whispering in the dark, all of a sudden, died away. The magician took a step forward, stopped, turned round and looked at her.
If you're afraid, turn back.
That door mustn't be opened. You know that.
I do.
But you're still leading me there.
If you're afraid, turn back. You still have time to turn back. It's not too late.
And you?
For me, it is."
This is another vision I am interested in deciphering. One possibility is that maybe 'Yennefer' was actually destiny leading her towards her inevitable fate. What about the last part though?
"You still have time to turn back. It's not too late" "And You?" "For me, it is."
My theory falls apart here, because I don't see how it can be 'too late' for destiny.
And what about the door that 'mustn't be opened'? Any ideas?