Just how powerful is Mirage Arcane?

[drewmighty]

So There was a tweet from crawford stating that you can drown people in the illusions. The illusions are basically real, so If I turn an area into a lake of lava does that do fire damage to people in it? It says the illusion takes the general form as well, however structures have no limits. Could I surrounda town with a wall and in turn fill it with water? I know Jeremy Crawford wrote a tweet stating that the illusion can drown people, and was thinking this seems super powerful. Just trying to figure out limitations to the spell. I know it is a 7th level spell, so I know it is super powerful, just trying to figure out how powerful. Thanks!

[MaxWilson]

So There was a tweet from crawford stating that you can drown people in the illusions. The illusions are basically real, so If I turn an area into a lake of lava does that do fire damage to people in it? It says the illusion takes the general form as well, however structures have no limits. Could I surrounda town with a wall and in turn fill it with water? I know Jeremy Crawford wrote a tweet stating that the illusion can drown people, and was thinking this seems super powerful. Just trying to figure out limitations to the spell. I know it is a 7th level spell, so I know it is super powerful, just trying to figure out how powerful. Thanks!

That's a great question. It is extremely unclear to what extent Mirage Arcane even qualifies as an "illusion" and not a temporary, enchanted reshaping of local terrain. If a creature with Truesight still drowns in the "illusionary" water (per spell text's description of the interaction between Mirage Arcane and Truesight), is it really illusionary at all?

As a DM I would be inclined to just rule that it's an invocation of a parallel universe and not really an illusion at all. I'd make up some magico-technical reasons why it gets classified as illusion magic and why truesight shows you the original terrain, but functionally I'd just treat it as a limited-scope Alter Reality spell a la AD&D. Either that or I'd rule that it is entirely in the mind and doesn't really affect you physically at all (including no drowning). Both options are valid, so I'd probably consult the players first before choosing how we want the spell to work in a given campaign.

[Segev]

Reading it, it lacks the text I was going to use to say it can't do that. Nowhere does it say its created terrain can't cause harm.

It really is more "temporarily alter landscape" than an illusion, then. That's amazingly good. Seems like you could, in fact, put an erupting volcano on top of a town and burn it to the ground. This makes the illusionist with Malleable Illusions even better, and I already thought it was pretty spectacular with this spell. Sure, Mordenkainen's Magnificent Mansion is extradimensionally protected and comes with servants, but mirage arcane can also provide quite the nice place to stay. Plus alter other terrain features to your liking. And, with Malleable Illusions, you're a miniature reality-altering god in your little demesne.

[Jacob_Wolf]

If a creature with Truesight still drowns in the "illusionary" water (per spell text's description of the interaction between Mirage Arcane and Truesight), is it really illusionary at all?

As I see it, creature with truesight can choose to or not to drown. In the description of the spell is said, that creature with truesight can still physically interact with the illusion. Not must. So if it so chooses, it will neither drown, nor be slowed nor silenced by water.

But here's what I'm not sure of. When you change a river into a lava stream, will it burn non-living stuff? Illusion affects mind, so you believe that you're drowning, burning, or even scaling nonexistent steps, that's cool, I get it, but what about an arrow? Arrow doesn't really have mind to be affected, so would it just go through the illusion? Because the spell description says that you can make something feel different. And I'm not sure about your ranger's arrows, but those in my game don't usually feel anything.

[Segev]

As I see it, creature with truesight can choose to or not to drown. In the description of the spell is said, that creature with truesight can still physically interact with the illusion. Not must. So if it so chooses, it will neither drown, nor be slowed nor silenced by water.

But here's what I'm not sure of. When you change a river into a lava stream, will it burn non-living stuff? Illusion affects mind, so you believe that you're drowning, burning, or even scaling nonexistent steps, that's cool, I get it, but what about an arrow? Arrow doesn't really have mind to be affected, so would it just go through the illusion? Because the spell description says that you can make something feel different. And I'm not sure about your ranger's arrows, but those in my game don't usually feel anything.

It doesn't actually say the illusion affects your mind. The illusion is probably closer to a hard-light hologram than a figment of imagination. Especially with mirage arcane.

[PhantomSoul]

It doesn't actually say the illusion affects your mind. The illusion is probably closer to a hard-light hologram than a figment of imagination. Especially with mirage arcane.

A fun way to flavour it might be given by the Creation spell:


You pull wisps of shadow material from the Shadowfell to create a nonliving object of vegetable matter within range: soft goods, rope, wood, or something similar. You can also use this spell to create mineral objects such as stone, crystal, or metal.

That same "Shadow Material" could be used by Mirage Arcane, which justifies it being Illusion (rather than Conjuration or Transmutation, perhaps) and which could justify just saying "it's a temporary real thing, so Creatures with Truesight can* still (physically and sensorially) interact with and see the 'Illusion'".

_______
* It's not that they "must", unless someone also casts Sympathy or otherwise causes them to be forced to interact somehow!

Edit: Messed up italicising. How embarrassing!

[Jacob_Wolf]

It doesn't actually say the illusion affects your mind. The illusion is probably closer to a hard-light hologram than a figment of imagination. Especially with mirage arcane.
Oh, now it makes more sense. So arrow would be always stopped by MA illusory wall, even if you had truesight. That's cool.

But still, can hologram, hard-light or not, burn a house?

EDIT:
That same "Shadow Material" could be used by Mirage Arcane, which justifies it being Illusion (rather than Conjuration or Transmutation, perhaps) and which could justify just saying "it's a temporary real thing, so Creatures with Truesight can* still (physically and sensorially) interact with and see the 'Illusion'".
Yeah, that's also cool, but just partially answering. Can the shadowstuff burn? Because burnt house is not really temporary thing...

[PhantomSoul]

From the examples, "a giant lake of lava" and "random fire" probably aren't intended to count as "terrain", but this seems like it enters DM territory. (Especially with "niche" cases like "the field that the Fire Elementals are on is now a lake.")

Reasonably, the spell doesn't it directly harms, so those sorts of effects wouldn't work. It's up to the DM, though, for specific cases it seems. Of course, watch out, since abusing the spell means enemy spellcasters could too... :)

[MaxWilson]

It doesn't actually say the illusion affects your mind. The illusion is probably closer to a hard-light hologram than a figment of imagination. Especially with mirage arcane.

"Smoke me a kipper, skipper." :)

[Ganymede]

I've always imagined that this spell creates a bunch of quasi-real, force-like magical fields that are then filled in with sensory information, and that seeing through the spell allows you to interact with these fields at your discretion.

Crawford's tweet opens up a whole new world of WTF with this spell.

[Segev]

Crawford's tweet opens up a whole new world of WTF with this spell.

It really, really does.