system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] Could a sufficiently powerful necromancer communicate with the disembodied spirit of Sauron after the destruction of the One Ring?

""If [the Ring] it is destroyed, then he will fall, and his fall will be so low that none can foresee his arising ever again. For he will lose the best part of the strength that was native to him in his beginning, and all that was made or begun with that power will crumble, and he will be maimed for ever, becoming a mere spirit of malice that gnaws itself in the shadows, but cannot again grow or take shape. And so a great evil of this world will be removed.""
—The Return of the King, "The Last Debate"   

Sauron is reduced to a spirit. Which I sort of take to mean a ghost, but even less able. Perhaps a mind and a will completely bereft of anything else. In this case it's possible that someone could commune with him to get some secrets. However, if Tolkien meant "spirit" as in *all that is left is what he did and nothing more,* then it shouldn't be possible. (At least, not as far as I can tell.)   

What say you?
gpt
Possibly. We know from *Laws and Customs of the Eldar* that necromancers (aside from Sauron the Capital-N Necromancer) are a thing. The way most dark magic like that works is to give some sacrifice of power to the being, allowing it to interact with the world again. Whether it's a sliver of your soul or something else, like the destruction of something beautiful or powerful, this foul sorcery requires a sacrifice to give the spirit enough power to interact. 

Your first instinct is correct: with the Ring destroyed, Sauron is reduced to a shapeless, powerless consciousness. Sauron's problem post-War of the Ring was that he had no power left whatsoever with which he could interact with the world, but he could not die because Ainur are tied to the world after entering it. A grant of power from someone like a necromancer could allow him to speak again, yes. It would be a very, very bad idea though, because Sauron is likely to attempt to take as much as he can get, and not be a very pleasant conversational partner. Imagine just being a disembodied mind whose only remaining emotion is hatred... and then some foolish necromancer summons you to tea.

>It is therefore a foolish and perilous thing, besides being a
wrong deed forbidden justly by the appointed Rulers of Arda, if
the Living seek to commune with the Unbodied, though the
houseless may desire it, especially the most unworthy among
them. For the Unbodied, wandering in the world, are those who
at the least have refused the door of life and remain in regret and
self-pity. Some are filled with bitterness, grievance, and envy.
Some were enslaved by the Dark Lord and do his work still,
though he himself is gone. They will not speak truth or wisdom.
To call on them is folly. To attempt to master them and to make
them servants of one own's will is wickedness. Such practices
are of Morgoth; and the necromancers are of the host of Sauron
his servant.

-*Laws and Customs of the Eldar*