Necrotech_Master wrote: »those target markers like the blue box are built into the base ESO game, i think since U36 at least
(on pc) you apply them by holding tab and using the wheel to select a marker (if you have your reticle targeting something it applies the marker to the target, if you are not targeting anything you apply the marker to yourself)
if you had a screenshot it might be helpful to confirm if this is indeed one of the built-in target markers