I just finished the third book, and I have to say, Elene's death ripped me to pieces.
While it's never clear there is a God orchestrating things, Elene believed fervently there was and this force held all her trust and she gave her whole being over to serving it.
Elene was the kind of person who wanted to help make the world a better place and yearned to be an important role; she was willing to sacrifice herself for others and the God she believed in. As she told Kylar: when Kylar died the first time Elene asked this God to take her life in exchange and she heard this force reply. First came for and took Sara. The second it came and took Mags. And then it took Elene.
I can't help but not place myself in Kylar's place and decide, "What would I do?" My love, my everything, just died. Not only this, but I was placed in a role where I had to be the one to push the sword into her? What would I feel about her God, who orchestrated this to happen and the world afterward for that matter? The answer is that I would not want to live in the world like that with a God like this. I would follow Elene.
Elene asked, please don't have such pride that you won't accept my sacrifice. I respect her wish if it's truly what she wants, but how would I ever be able to know if she was asking for herself or for me and others. She asked, wouldn't you sacrifice your baby for all these great people? "No!, no." And I agree with him, I would not do it for them or for me; I would only do it for her.
I think the only thing that would keep me from following Elene would be if perhaps Vi realized what I was going to do and stopped me and asked me to wait. To at least wait until she was sure about something (Kylar's, and thus Elene's child would have a life, a life that Elene would have wanted Kylar to protect and be a part of.)
But I do know one thing, if I died one more time, I would be walking swiftly through the small door without a backward glance, never to return, never again to take a life of someone I loved. Never, ever to take a life on a 'What if?', 'What if that one life sacrifice could save more and everyone?' No! The means justify the ends, not the other way around; you get monsters if you do it the other way. Kylar might be the judge, but it is another thing to take lives on what-if's; doing so enters the territory of what the Godkings were, what Dorian was starting to do at the end in taking jenine's decisions from her.
Elene will never live a life beyond youth. Elene will never be the mother of her child. Never watch her child grow, much less see her child. Never grow old with and have a life with Kylar. I'm angry at the God Elene believed in. She gave everything she had to it and everyone else, and aside from one short season of happiness with Kylar and a short important role, it decided to take everything from her. I am beyond anger. Vi looked over at Kylar and saw him calm, saw him at peace. How? I can't understand; the only way I could feel that way at that time would be in the wake of making the decision: a god like this or Elene? Elene.
One thing about your statement of you would walk through the small, wooden door is that it isn't possible. This is due to the fact that he chose to remain immortal it wasn't tha Ka'Kari it was him. Also, Elene would of died regardless of whether or not Kylar killed her per the Black Ka'Kari's magic. So in the end her sacrifice was made worthy and that was why Kylar was at peace.
I would be temped to agree with Dylan, but only add, that Elene too made choices.
Throughout the books she was depicted as helpless, vulnerable, and entirely too naive for the world in which she was born. She existed only because others looked after her, first Azo, then Jayo, then Kylar (in defiance of his master), then the Cromwells, and finally Kylar again. She does however get progressively stronger, although still needing support throughout... until the end!
She made no real choices for herself until she was forced to go and save Uli, and then seemed to blossom into a complete character with the sort of strength that all the others in the book seemed to have from day one. Arguably that strength continued to build, until it was her supporting others, and forcing others (in particular Kylar) to fight the final battle. The strength to contain a virtual god is way beyond what others in the book were capable of, and her sacrifice in the end made victory possible.
So why was Kylar at peace in the end... bare in mind it was Elene's will if not her strength (that came from the others, and the watcher in the woods!) that made the transformation of the city possible, her love and compassion were a big part of that, and Kylar was connected to it as well. wouldn't it be just like Elene to ensure that Kylar, an immortal with an enormous soul weight to bear, was able to deal with his grief, and didn't Elene say very clearly, that she wanted Kylar to look after Vi, paving the way for a further relationship with a woman that would support Kylar going forward. She was trying to prevent Kylar becoming a monster!
Bear in mind too, that if Kylar did decide to test the immortality to destruction, he might kill those whom Elene herself loved, not least her own child...
Elene is far from a tragic character in my opinion, she is cut from the same mould as Sturm Brightblade in the Dragonlance series, and therefore a necessary counterpoint to the other heroes and villains in the book.