Orphan's memories:  There was a wizard book she stole about this.  It had NUMBERS.

...possibly these numbers were literally just the generalization of Euclidean distance to N dimensions, but Orphan had stopped reading at that point.  Her sorcerous practice regarding this general idiom was "keep my spells inside the standard three dimensions and shield anything that tries to come at me from outside it".

Orphan's memories:  There was a wizard book she stole about this.  It had NUMBERS.

...possibly these numbers were literally just the generalization of Euclidean distance to N dimensions, but Orphan had stopped reading at that point.  Her sorcerous practice regarding this general idiom was "keep my spells inside the standard three dimensions and shield against anything that tries to come at me from outside it".