Nicky was trying to break Ivy, it is possible her mothers suicide indicates this. At that point Nicky has a Rasmussen? style host, the body effectively run by a Fallen in a total abdication of free will to the Fallen.
At that point Nicky has a Fallen Archive with no pesky free will. The Fallen absorbs the entirety of the information of the Archive (all recorded information of humanity to date, even that previously destroyed ) and the host body is then superfluous.
The question is - what was Nicky looking for in the Archive? Information lost or obscured even from Anduriel? What information would justify him being thrown out the Accords and having the entire supernatural world at his throat? Was he looking for clues to the whereabouts of the Spear? He risked his daughter for that. Did this give the opening for him to be set up in Skin Game? Uriel is an intellectus, he would know what they were interrogating the Archive about, he could do nothing about it and Nicky would know this, indeed glory in it, he had done what he could already do in granting Harry Soul Fire. Nicky wouldn’t know Mab was already working with Uriel, the use of Kringle as a go-between was an established thing, an open route for information probably thought limited to Christmas rather than an information route directly into Winter. Mab and Uriel may have burnt this particular route with Nicky now with the benefit of hindsight. He knows he was had. Thinking about it Mab knew she had spies in her court (Nameless) so using Kringle prevented Anduriel or Nameless finding out about the contact and the flow of information, especially Odin is a security expert - as Kringle he provided a secure back channel.