Kaisoku |
Duration is instantaneous, so nope, not dispellable.
However, Wish will usually work (I wish this place wasn't unhallowed, etc).
You can cast Hallow over top of Unhallow though.
Instantaneous Effects: Two or more spells with instantaneous durations work cumulatively when they affect the same target.
Casting Hallow in the area will negate the channeling effects, and provide equal protection magic (protection vs evil). You could even have a similar but opposing spell cast to suppress the effects of the tacked-on spell (depending on how it's set up). Like, if they have Bane set up with the unhallow, you can put Bless, etc.
Good people still won't be able to mind control a person in there though, as there's nothing that'll get rid of that really.
Since it takes 24 hours to set up, and has a costly material component, it's adequately difficult to counter this. Note that it's only a 40' radius normally as well (although there is widen spell metamagic).