Season 12
Enormous tower discovered being built inside the Octurne at the end of Season 12. Aluvyn’dralor was at the top. It fell when the Octurne broke apart and speared into the world in the far north, where it slowly made itself the new north pole and oriented itself toward the sun (dragging the world with it) and forced the planet to be tidally locked.
Season 13
In Season 13, Esmund figured out that its arrival disrupted the working of the Memento, which kept Queen Lil’lith alive by securing reality, and that disruption was causing the cascading failures of reality.
One purpose of the White Tower is to open portals for use by whoever controls the tower to change our world into something they want. (Note from DM: The White Tower may possess functions beyond interplanar transportation.)
White Tower’s Impact: Desmun’s and Esmund’s studies reveal increasing chronomantic uncertainty linked to the White Tower’s arrival. The Tower’s disruptions are breaking down time, reality, and the weave, allowing the impossible to annihilate reality. It is getting worse, and it will grow increasingly worse until reality itself has completely broken down and collapses.
Season 14
In Season 14, is at the center of the White Crown, the city of Angels that surrounds it. There are no records of the tower and the city never existing; as far as this world is concerned, there has always been ~~~war~~~ the Tower in the north.