The Night King's Elaborate Plan:
In order for this theory to be plausible, The Night King must have magical abilities of "necromancy" AND "the sight." Through fires/dragonglass magic, he can see/speak/command visions in the flames (like what happened to Varys). Both of these abilities can see glimpses of the future, while the other one can raise and bring the dead back to life.*
Let's take a look at the evidences:
1) Necromancy: All the wights, the undead polar bear, the Hardhome episode, and Beric/Jon's resurrection.
Necromancy also means "the act of communicating with the dead in order to discover what is going to happen in the future."
2) The Sight: The Night King sees Bran and grabs him during his vision. Bran sees and talks to Jojen Reed in their visions. They both have "the sight."
3) Flames: All the visions the characters saw are about going to the North/battle in the snow, bringing the dead to King's Landing, or fulfilling the prophecy—bringing Jon Snow and Daenerys together.
In his plan, all the decisions by the characters are their own, but he vaguely showed them visions (Melisandre, Thoros, The Hound, & Tyrion) and willingly helped dead characters back to life (Beric & Jon Snow) to influence their decisions (Davos & Jon), their ideas (Tyrion), and his elaborate planning going forward—setting a trap for whomever (Jorah, Jon, Tormund, The Hound, Beric, Thoros, Gendry) would go beyond the Wall and capture a wight ("bring the dead to her") and then seek Daenerys for help.
To ensure the chain of events works, he purposely let characters go (The Night's Watch, Lord Commander Jeor Mormont, & Samwell Tarly) to spread the news so that eventually, someone (Bran, Jon Snow or Gendry) will pass on this threat ("We need to send a raven") to Daenerys, so she can finally fly beyond the wall, and that's the time the Night King (who saw these future visions) can ultimately acquire an undead dragon AND destroy the wall.
"The past is already written. The ink is dry." The Night King is the Lord of Light. And in the end, *no one* is going to kill the Lord of Light.
*Taken from the original description of "The Night's King Elaborate Plan" video (the full version, which is currently in private).
The magnificent seven and their wight hunt was also a parallel to the opening prologue in the first episode (full version is private—going to edit a new version): https://youtu.be/rzk17BWVycA