XMarker

From The Elder Scrolls Construction Set Wiki

There is a Static called "XMarker" which is used very often in the game and appears to have special properties, or at least special uses - would someone care to describe their uses?

A cursory search for the term "Marker" revealed a few articles that mention it (MoveTo, this Solution), but nothing specifically about it. Searching for "XMarker" refined the search somewhat, dropping some extraneous matches, but still nothing that more than mentions them.

Leviathan62089 writing in reguards to your question about Xmarkers.

The Xmarker is a simple object used for a multitude of things. They appear invisible in the game and record X,Y,Z coordinates. Xmarkers are also always persistent references(scripts can always refer to them). Say for instance you want your guard to patrol between to, three, or four different locations. You can utilize Xmarkers as a waypoint at each location you want your guard to travel to, then using packages you can set those Xmarkers as locations. You can also use the X,Y,Z coordinates for an Xmarker, if say you want an object to appear at a specific location at a specific time(through script). Xmarkers can also be used as a trigger, some quests like Cropsford(MS46FIN) parent initially disabled objects to Xmarkers and then when the time comes enables the Xmarker, and as a result enables all child objects under that marker. The standard of use for the Xmarker though is simply to record X,Y,Z coordinates and to act as a reference for scripts.

There is another type of Xmarker known as an Xmarker Heading. The Xmarker Heading object has all of the functions of an Xmarker, but also records the rotation of the marker. These are primarily used as a location and direction NPCs use to perform a function. When you see an NPC training with anything from swords and axes to bows and spells, they're using Xmarker Headings and packages.

Hope this helps. -Leviathan62089