You create a ward against magical travel that protects up to 40,000 square feet of floor space to a height of 30 feet above the floor. For the duration, creatures can't teleport into the area or use portals, such as those created by the gate spell, to enter the area. The spell proofs the area against planar travel, and therefore prevents creatures from accessing the area by way of the Astral Plane, Ethereal Plane, Feywild, Shadowfell, or the plane shift spell.
In addition, the spell damages types of creatures that you choose when you cast it. Choose one or more of the following: celestials, elementals, fey, fiends, and undead. When a chosen creature enters the spell's area for the first time on a turn or starts its turn there, the creature takes 5d10 radiant or necrotic damage (your choice when you cast this spell).
When you cast this spell, you can designate a password. A creature that speaks the password as it enters the area takes no damage from the spell.
The spell's area can't overlap with the area of another forbiddance spell. If you cast forbiddance every day for 30 days in the same location, the spell lasts until it is dispelled, and the material components are consumed on the last casting.
* - (a sprinkling of holy water, rare incense, and powdered ruby worth at least 1,000 gp)
Can you teleport out?
Yes, it only blocks travel into the warded area. Not out of it.
Are there any spells that would block teleporting into and out of a large area?
Private Sanctum: https://www.dndbeyond.com/spells/private-sanctum
Forbiddence is 40,000 square feet which is 200x200 (up to 30ft above ground level) at level 6. Private Sanctum, cast at level 6, would be 300x300 for 90,000 square feet, and cover a 300ft area up as well. The biggest difference is that Forbiddence allows you to use the 40,000 square feet in weird arrangements (and does damage). Also, nothing stops you from casting both in the same area. So you could have Forbiddence for blocking entry for specific kinds of creatures and Private Sanctum for blocking Divination and teleportation/planar travel into and out of the area. Also, Forbiddence is a Cleric spell and Private Sanctum is a Wizard spell so which you'd likely use depends on what kind of person is casting it.
Interesting question. With the spell teleport it states "This spell instantly transports you and up to eight willing creatures of your choice that you can see within range, or a single object that you can see within range, to a destination you select." So if one of the willing creatures was a celestial, elemental, fey, fiend, or undead it would trigger the damage effect unless there was a password mentioned.
Now I'm an old player from when D&D first started. Spells like Dimension Door, Blink etc when you cast them, you temporarily stepped into the ethereal plane like a phase spider, blink dog etc and then pop back. Now in 5e they done away with this dynamic which I still like and will homebrew it at my table but its your choice as DM how you rule it.
Does this forbid the opening of bags of holding or other extradimensional spaces?
The spell explicitly states that it prevents teleporting into the affected area
if they know the password it doesn't matter their type correct?
yes
The only mention of consuming the materials is in the 30 day version.
Does that mean that you could cast it on a given day, and as long as you didn't recast it for 30 days, you would keep the materials?
Other spells like Revivify explicitly state that the material component is consumed.
Not only can you cast it every day up to the 30th day without the components being consumed, but, since it's a ritual spell with a 10-minute casting time, you can cast it 144 times per day. That would cover 128 acres, or more land than the Magic Kingdom at Disney World.
Oh god, thank you for this post! I am preparing to run GoS and I would pannick if one of my players done something like this.
Maybe if you have 144 spell slots, I don’t know what character would ever have 144 spell slots though
It's a ritual spell, so it won't consume any spell slots. However, I just realized that casting Forbiddance as a ritual would take 20 minutes (casting time + 10 minutes), so I guess the upper limit would be 72 times per day. So, you can only cover 64 acres. Still, not bad!
forcing you to touch all affected squared would probably be the best thing in terms of ensuring the intent of the spell (ie being used to protect your own castle, instead of using it to completely destroy every dungeon)
Wouldn't always punish your players like that
Would this work on a ship, a moving ship?
So an interesting thing with this we discovered in my game: Tome pact Warlock, got this as a ritual. He's fiend pact so now he has *twice managed to hurl a big enemy into hell while they were in the area of a forbiddance spell. The nearest unoccupied space ends up being....30ft in the air above the area. :D
It takes ten minutes to cast. I know it doesn't say the following in the spell description, but someone casting this spell needs to walk around and through the area that they are casting it on while they cast the spell. Kinda like a priest blessing a building or home using a holy censor. This is a warding spell, not a weapon of mass destruction. Points for creative thinking though.
Actually since it's a ritual (so the party could try to re-cast it) the better solution might be to just cast your own forbiddance spell, as two of them can't overlap.
Since we can assume bad guys set up their defences in advance, you can decide that it was cast for the full 30 days so is permanent. Worst case, the party needs to use dispel magic to get rid of it, in which the bad guys might also tie something else to that happening, e.g- one or more magic mouth(s) to sound the alarm. Basically put one at every entrance triggered to go off if an attempt is made to dispel it, then put more through the lair which are triggered if any other mouth activates; instead full lair warning siren. 😉
You might also assume the big bad casts forbiddance at the highest level they can in order to make it as hard to dispel as possible; strictly speaking they could cast it as a ritual for 29 days, then only burn a single high level slot on day 30 to make it a permanent spell at that level (so 7th-, 8th-, or 9th-level instead of 6th). This way the party either needs to burn the same level of dispel magic (with no way to know that forbiddance was upcast) or beat the check, which you've now made as hard as possible (DC 17-19).