Except you don't cast it on any object or creature, you cast it in a 20 ft cube and everything that qualifies (object or creature) is lit up.If you want to cast fairie fire on a large rock in a field, that's fine.
If you want to cast the spell on the terrain in general no. The terrain is not a discrete object.
Except you don't cast it on any object or creature, you cast it in a 20 ft cube and everything that qualifies (object or creature) is lit up.
But what if I casted fire fairie would they rock on? Or just be depressed in a potters field?If you want to cast fairie fire on a large rock in a field, that's fine.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.