Once your character is in the location you want to use as an "anchor point" for CR purposes, you can simply call:
Code:
AreaStateCache.Current.ResetCurrentAnchorPoint();
However, you have to figure out "where" that position exactly is. This game uses random map generation, and the exact coordinates are not the same most of the time since the levels change.
One idea, is once you are on the top tower floor, you check for the Dominus object:
Code:
var dom = LokiPoe.ObjectManager.GetObjectByName("Dominus, High Templar");
If that object is not null, you now have his position, so you can just choose a position around him, or one of his bosses to use as your "fallback" position.
For example:
https://db.tt/UWO6wJhr
If you use the location of Flamebrand, Sparkfist, or Biterblade, it should be "close enough" to that location.
Remember for the last phase of the fight, you have to run closer to the stairs to trigger his last form.
If you're looking to try and code that boss fight logic, I'd suggest taking a high level character to Normal, and make sure you use the Object Explorer under Tools, so you can check object names and various Auras to help you along the way.
