This spell had two major effects that operated on a volume up to one 60 ft (18.3 m) cube per level of the caster.[note 1] The area could take any contiguous shape the caster desired as long as the maximum volume was not exceeded.
The first effect was to block all extraplanar movement into or within the protected area. Creatures could not use teleport, dimension door, plane shift, or any other mode of travel through the Astral or Ethereal Plane to enter, move from one spot to another, nor be summoned into the area. All such attempts simply failed.
Forbiddance also attacked individuals and creatures that crossed the barrier into the protected area based on the difference in alignment with the caster. Creatures of the same alignment suffered no damage. Creatures that differed in either the good/evil or law/chaos aspect of alignment were smitten harshly as they entered the forbidden area. Those that differed in both good/evil and law/chaos were doubly rebuked. At the time of casting, the priest could set an optional password that allowed friendly beings of different alignments to enter the area unharmed as long as they spoke the password as they entered.
The older version of this spell had more stringent requirements but was better at keeping the unwanted out of the affected area. A prerequisite for casting forbiddance was that the area be consecrated, presumably to the same deity that the caster worshiped. Next, more weight was given to the good/evil axis of alignment than the law/chaos axis, and therefore this spell did more damage to the former and less to the latter. And last, when the older version set a password, it was proof against anyone, friend or foe, from entering the protected area for the duration of the spell. This was also true for those who attempted to breach a non-passworded barrier and failed to overcome the magic of this spell.
Verbal and somatic components were required, plus rare incense had to be burned and holy water sprinkled about the area. For a password to be set, even more incense had to be used. The estimated cost of incense for a 60 ft (18.3 m) cube was 1,500 gp (only 1,000 gp for the older spell). The extra incense for adding a password cost another 1,000 gp plus 1,000 gp per cube (5,000 gp for the older spell).
- For comparison purposes, a 6th level cleric could protect a volume bigger than the Washington Monument.
- Mike Mearls, Jeremy Crawford (2014). Player's Handbook 5th edition. (Wizards of the Coast), pp. 208, 243. ISBN 978-0-7869-6560-1.
- Rob Heinsoo, Andy Collins, James Wyatt (June 2008). Player's Handbook 4th edition. (Wizards of the Coast), p. 305. ISBN 0-7869-4867-1.
- Jonathan Tweet, Monte Cook, Skip Williams (July 2003). Player's Handbook v.3.5. (Wizards of the Coast), p. 232. ISBN 0-7869-2886-7.
- Ed Greenwood, Sean K. Reynolds, Skip Williams, Rob Heinsoo (June 2001). Forgotten Realms Campaign Setting 3rd edition. (Wizards of the Coast), p. 63. ISBN 0-7869-1836-5.
- Richard Baker, James Wyatt (March 2004). Player's Guide to Faerûn. (Wizards of the Coast), p. 87. ISBN 0-7869-3134-5.
- Matthew Sernett, Jeff Grubb, Mike McArtor (Dec 2005). Spell Compendium. (Wizards of the Coast), pp. 278–279. ISBN 0-7869-3702-5.
- Hal Maclean (September 2004). “Seven Deadly Domains”. In Matthew Sernett ed. Dragon #323 (Paizo Publishing, LLC), p. 64.
- David "Zeb" Cook (August 1989). Player's Handbook (2nd edition). (TSR, Inc.), p. 228. ISBN 0-88038-716-5.
- David "Zeb" Cook (April 1995). Player's Handbook 2nd edition (revised). (TSR, Inc.), p. 289. ISBN 0-7869-0329-5.
- Cook, Findley, Herring, Kubasik, Sargent, Swan (1991). Tome of Magic 2nd edition. (TSR, Inc), p. 154. ISBN 1-56076-107-5.
- Richard Baker (1996). Player's Option: Spells & Magic. (TSR, Inc), p. 187. ISBN 0-7869-0394-5.