It could be cast on any location, and if the location has a combatant in it, the location or the combatant.
This did not compute for me. I cannot rearrange it in any
way that makes sense to me. Here is my best guess at
The spell can be cast on any location. If no combatant is at
that location then the spell is anchored to that location and becomes
an area-effect spell.
If a character is at that location then the spell is applied to
that character and no spell is attached to the location itself.
It seems that maybe what would work is two spells, one of
which is used if the location is occupied and the other if the
location is empty. Is it like that?