You say "Not to be too literal about it" but then go all clinical on me. That simply will not do. This is Wagner cum Schopenhauer, not Grey's Anatomy
Isolde undergoes a Verklärung the nature of which permits her to all by herself become one consciousness, both Tristan and Isolde residing in the realm of Night. The music tells us that. What happens in the realm of Day thereafter is not our (or Wagner's) concern. Alice doesn't live there anymore.
The meanings of "death" and "transfiguration" are anything but clear in your explanations.
Tristan has died in a suicidal frenzy, without benefit of any "transfiguration." So he can't have gone to any "realm of Night," unless the realm of Night is simply oblivion (which is in fact the way he describes it to Kurwenal - Urvergessen
, complete forgetting). But sheer oblivion would just be ordinary death, in which case Isolde's only way of "uniting" with him would be to die as well. If Isolde does not die, how is it that she becomes "one consciousness" with Tristan who, being stone cold dead, has no consciousness to become "one" with? You could posit that death is not "complete forgetting", and that Tristan has somehow, despite his physical death, retained some sort of consciousness capable of uniting with Isolde's. But then why not have Isolde too die, and follow Tristan's path into the realm of Night? The metaphysics of this are certainly unclear, and having Isolde remain alive seems inconsistent with any explanation.
If Isolde remains alive, she - the human being in the world - is going to have to get on with a life of some sort. You can call the matter "clinical" and say that it's none of "our" concern, but I'm not buying the idea that Wagner would leave a character hanging in such a metaphysical and existential limbo. Wagner's other "eternal femine" figures, from Senta to Kundry, all clearly die. The symbolism is consistent in his work: death is the form "transfiguration" takes in Wagner. Why should Isolde be the exception?
Fundamentally, I think it's a mistake to regard Tristan und Isolde
as a myth or fairy tale in which magical and otherwise inexplicable things happen. The characters in this opera are human beings - knight, princess, king, vassal, handmaid - and are not even treated as archetypes. Tristan
is really a domestic tragedy, but with a metaphysical overlay courtesy of Wagner-cum-Schopenhauer. There are no magical objects or occurrences, not even the so-called love potion, which doesn't cause the lovers' passion but simply occasions their confession of it. Nothing happens in this opera that hasn't happened and doesn't happen in real life, except for the way Tristan and Isolde use Wagner's/Schopenhauer's philosophical concepts to describe their experience to themselves. In such a context the idea of Isolde's "transfiguration" as anything other than a subjective experience is quite gratuitous. Tristan dies in Isolde's arms; beside herself, she imagines Tristan reviving and rising into the sky, she imagines glorious sensations of pleasure, she imagines herself drowning in them and going unconscious in a state of rapture - and then she dies. The words of her dying song say nothing about embracing Tristan or becoming "one consciousness"; her final words are unbewusst - hoechste Lust!
- "unconscious - highest bliss!" For her, unconsciousness, with Tristan unconscious beside her, is the highest bliss she could conceive, and certainly the highest her miserable life would allow her to achieve.
Tristan and Isolde could not bear to live apart in the cruel world of Day. Like all lovers, they dreamed of being "one." But knowing that that was impossible in the Day world, they could only identify oneness with death. And so they wanted to die together - to go to the realm of Night where the pain of being separate bodies and souls, forever separated, would be over - nicht mehr Tristan, nicht mehr Isolde.
They got their wish, but Tristan died before he could know it. Isolde remained to complete the fulfillment of their dream. She died to be with him, and her vision of ecstasy was life's final mercy on her, and its final blessing on their love. There would have been no mercy or blessing in forcing her to live on in the world of Day.
Wagner's music, after Isolde's final words, tells us the exact moment at which Isolde gives up her life: the last sounding of the "Tristan chord," a final reminiscence of the suffering of the lovers, which now resolves into perfect consonance and peace. And to the final deep, serene, organ-like chords in the orchestra, King Mark raises his hand gently over their bodies in benediction as the faithful Brangaene kneels beside them. Surely she is weeping silently.