Even before she has any use for him, long before she discovers even his name, Esther is there for him on the other side. He rips through screaming and crying out in agony with every death, his soul pulled nearly in two; and his time in the other side is filled with confusion and pain that seems his only companion. (Until he is wrenched back into his lifeless body, and reawakes without any sort of recollection).
But she comes to him, and cradles him in her arms, and sings to him the lullabies she once used to sooth her children (memories that would have been unbearably bittersweet, were they not so distant), and she comforts him and eases his torment with gentle words and soft hands that stroke at his brow (as if he were Henrick, serene in her arms with a peaceful stillness that could not quite be attributed to sleep) until he relaxes against her, clinging to her as if only she was the only thing that could tether him to sanity.
It is many more deaths before Esther realizes what she must do to him, and she hates it, despises it, for she has grown to see him as her child, and unlike her monsters he is untainted and good and alive, but she understands its necessity even as she resents it. She will have to taint him, have to corrupt him, have to twist him until he is nearly as unnatural as Niklaus and the rest, no different from her other abominations (except this one will be different, because his un-death will at least bring about a greater good).
It is not hard to remold him, she has seen him at his most vulnerable time and time again, and he has already told her all of his secrets (whispered to her over time as she has held him in his misery and pain), and in return she has confessed everything to him (told with the greatest of care, though he never remembers a single word) and so she shoves aside her tenderness for the man, and begins to precisely and methodically craft his susceptible mind and exposed soul into the weapon she needs (but does not want, can never want) him to be. It is easier than it should be, his hatred of vampires runs deep and only requires a little provocation to encourage it and raise it to the surface, and she does so with an almost artful subtly. She cuts away all of his light and humanity, until there is nothing left but inky darkness, growling with anger and begging for violence (it trembles with bloodlust, writhing with a palpable need for vengeance). And when it finally rises to play in the other realm, Esther knows she has succeeded.
She has forged her weapon, and she prides in her impressive accomplishment even as she grieves the passing of the man she was forced to murder (watching him from the other side brings her no joy, as she recognizes that Alaric Saltzman is already dead, and all that is left is the unadulterated darkness of his spirit, half-awake and wearing a twisted mask).
And when she sends the Bennet witch to complete her mission, and it sloughs off the remainder of its Alaric-skin without a second's hesitation, she cries out in horror at what she has wrought, even as a genuine smile begins to form helplessly over her lips (for it almost reminds her of a diamond, pristine, exquisitely carved, and glittering with hate and cold-blood determination, nothing but sharp edges and radiant blackness). And Esther feels fulfilled (and now her new child will kill the rest of her children) and then wonders where this one will go when he dies, again.