Can Hallucinatory Terrain hide altered terrain?

[Cheesegear]

Can Hallucinatory Terrain affect structures inside natural terrain?

Can HT be used to disguise a 'Hobbit hole', or a mine? Could you dig into a mound, or a hill/mountain, build inside that mound/hill/mountain...And then hide the mound entire?

[Silly Name]

So, the relevant language is this bit from the spell's description:


Manufactured structures, equipment, and creatures within the area aren't changed in appearance.

I guess an argument can be had about what counts as a "manufactured structures", but in general if the structure itself is not being "altered", then I see no reason why you couldn't alter the appearance of the terrain in a way that would obfuscate buildings and the like as long as you don't try to directly alter the manufactured elements, but rather hide them behind natural-looking illusions.

For example, imagine you have a small shack on the barren top of hill, and you want to hide it. You could very well cast Hallucinatory Terrain to make the hilltop look like it's full of trees, and place the trees and plants in a way that could hide the shack from sight unless closely inspected.

For the mine, you could "place" a very big rock in front of the entrance, or if you have a hole in the ground you could create the appearance of a bubbling swamp on top of the hole...

[JLandan]

A lot depends on what is "natural" terrain and what is manufactured. For example: a natural cave is natural terrain, but a mine entrance is manufactured, even though they may appear similar.

And a disguised mine entrance is still manufactured, more so really.

HT can provide cover for a manufactured element, but cannot alter the element's appearance.

[Keravath]

As with all illusions, a lot depends on the DM ruling.

Here is the spell text:

"You make natural terrain in a 150-foot cube in range look, sound, and smell like some other sort of natural terrain. Thus, open fields or a road can be made to resemble a swamp, hill, crevasse, or some other difficult or impassable terrain. A pond can be made to seem like a grassy meadow, a precipice like a gentle slope, or a rock-strewn gully like a wide and smooth road. Manufactured structures, equipment, and creatures within the area aren’t changed in appearance.

The tactile characteristics of the terrain are unchanged, so creatures entering the area are likely to see through the illusion. If the difference isn’t obvious by touch, a creature carefully examining the illusion can attempt an Intelligence (Investigation) check against your spell save DC to disbelieve it. A creature who discerns the illusion for what it is, sees it as a vague image superimposed on the terrain."

Manufactured structures aren't changed in appearance ... but roads are. So roads are manufactured but aren't classified as structures.

Also, note that in the spell description - every example changes the visible terrain to another type of visible terrain. The spell mentions nothing about adding elements like trees, bushes or large rocks.

- open fields or a road can be made to resemble a swamp, hill, crevasse, or some other difficult or impassable terrain
- A pond can be made to seem like a grassy meadow
- a rock-strewn gully like a wide and smooth road

The intent would seem to be to allow the spell to change the appearance of just the terrain itself (i.e. the ground or surfaces) - not create an entirely illusory scene. Looking at it from that perspective - the constraint on manufactured structures, items and creatures makes more sense. You can't create an illusion to hide them because they are not terrain. You couldn't add trees or a large rock in front of the structures since otherwise you could create any sort of image you want a couple of inches from the structures and hide them that way - what is the difference between changing the appearance of an item or creating an image an inch away from the item that effectively changes its appearance.

On the other hand, Mirage Arcane uses similar wording except it can change the appearance of manufactured structures as well as adding them. Since it can add structures, I think it would be able to add trees and other elements. Hallucinatory Terrain says nothing about adding elements to the scene.

Anyway, this is another example of why illusions are always a DM call - the spell description just doesn't give enough information to decide exactly what can or can't be done with the spell - so if you want to do something with an illusion - check in with the DM to make sure that you both think it should work the same way.

P.S. Just to emphasize the need for DM adjudication.

1) If a creature/character turns a rock filled gully into an illusion of a wide open road - could creatures be hidden behind the rocks which are hidden by the illusion? The illusion doesn't affect creatures but if they are behind a rock that is hidden by an illusion - can they hide there?

2) Can a crevasse be changed into an illusion of an open field? (open fields can be changed to look like a crevasse ... so presumably the reverse is true?)

3) If you have a building at the bottom of a crevasse that you make look like an open field - can it be seen if someone looks at the open field illusion?

4) A pond can be made to look like a grassy meadow ... are the creatures swimming under the water in the pond visible? Are waves or other water disturbances hidden? Can the sound of waves be heard or does the illusion replace the sound of waves with the sound of grasses blowing in the wind?

Illusions require a ridiculous number of DM rulings :) ... best to ask the DM about their use.

[Psyren]

As noted, Mirage Arcane - a more powerful spell - does this. That is usually a pretty good indication that the weaker spell shouldn't.

With that said, you may have some leeway in determining when a hole in the ground becomes "manufacturerd."

[Segev]

I suspect that, while you couldn't "disguise" a man-made cottage, for instance, you COULD turn a valley into a pond. And if the cottage happens to be at the bottom of the valley, it probably isn't visible with the pond covering it. So you probably cannot turn a man-made hole into anything else, but if the illusory swamp covers the ground where it's dug, it's still probably hidden.

There's a lot of "ask your DM" in the limitations. Personally, I'd allow trees to be added or subtracted. I would draw the line at tree houses. As long as it's a "general terrain" thing, it's probably fine.

In one game I was in, the DM allowed another player to use hallucinatory terrain to create a huge iceberg floating in the water, totally surrounding our boat, so that we were obscured. (It was northerly enough that icebergs were a thing.)