Azshara got the stone in 8.2, this much is clear. Why and how is not so clear.
In all likelihood the Illidari ultimately would have delivered the stone for Azshara.
The TL;DR version being, Azshara would have been smart enough to play both sides, and the common denominator is the Illidari. It is still currently UNKNOWN who, what or how Azshara obtained the stone, only that she did. What's more interesting than trying to prove this assumption is what, if true, it actually means since literally the decisions of this group cascade into saving Azeroth not just in Legion but also in BfA and Shadowlands.
What has been suspect for years has been the strange alliance existing between Azshara's / Vashj's naga and the Illidari.
The facts that have been known since WC3 are: (There's more to this list, but these are the basics.)
- Vashj is loyal to Azshara
- Illidan and Vashj, and by extension Azshara desire to destroy the Frozen Throne
- Vashj, by her decision, made the call to save the Belfs from the humans for unknown reasons
This being given, what was suspect in Legion was:
- Why are Coilskar fighting against the naga attempting to seize the tidestone in Legion and at the Tomb of Sargeras?
- Why does Azshara have reason to launch, back and sponsor a campaign against the Lich King?
- Why was it necessary to commit resources to save the Belves?
If it is the case that the Illidari delivered the Tidestone, it would mean Azshara herself foresaw the role the Illidari would play in both restoring the titan pantheon and taking down Sargeras, but also resolving and defeating Nzoth's corruption AND enabling Sylvannas' path into Shadowlands to correct and restore it.
While it would make sense for Azshara to play her hand with Illidan as a long play, it makes less sense for her to deal with Sylvannas since this risked everything in order to obtain Xalatath. Until you consider the survival of Alliance and Horde forces in this gambit hinged on obtaining the tidestone, to both set the trap AND keep the survivors alive. This also secured Xalatath in striking a mortal blow to Nzoth and limited the damage an extended engagement/ war with both the Alliance and Horde would bring.
Azshara is and has been a keystone role in Azeroth's survival, even in necessarily furthering Sylvannas' adgenda. Her vision, in all likelihood, doesn't stop with Shadowlands, whereas we know since day one she desires an end to the Frozen Throne period. In enabling Sylvannas, Azshara has provided the path to restoring the dramatic imbalance of sufferring in the Shadowlands which has been coopted and abused by the Legion via necromantic magic by hijacking death in bringing undead armies to Azeroth. Her actions demonstrably hit at all three threats against Azeroth: The Legion, The Old Gods, The Undead.
Azshara: Savior of Azeroth
Edit: Formatting