Mirage Arcane, Malleable Illusion, and Illusory Reality: Is this legal?

Question

I'd like to verify if the following is RAW. It's very pivotal to a game of mine.

1. An Illusionist wizard will cast Mirage Arcane, keeping the illusion of the area to be exactly the same as the area now. This conceals the presence of the illusion.

2. Fly over to the targets.

3. When they're in sight, use Malleable Illusions. All but one target will be surrounded by a single Adamantine dome that doesn't touch them, but it does separate everyone but one. Follow up with Illusory Reality, trapping everyone inside the dome in pitch darkness.

• Each Adamantine panel will have AC 23, HP 27 per inch of thickness. But there's nothing stopping the panel from being 10 inches thick, so the actual wall will have 270 HP.

4. Engage in a one on one fight with the target, win

5. Rinse and repeat

Alternatively, step #3 could have no Illusory Reality section, as Mirage Arcane is tactile anyway. It justifies the solidity (having AC and HP) of the dome wall more with that power used, though.

Answer 1

Yes.

Mirage Arcane is a spell that is 7th level. That is higher than first. Malleable Illusions would work on it. The dome is one object, so it can be made real for 1 minute. All seems legit.

And, it isn't as overpowered as it seems.

It might seem like it is overpowered, but at level 14 the things you are fighting should be able to break through a 27 HP wall in an action or two. Moreover, that isn't their only way out:

• Dig
• Etherealness
• Dispel
• Counter Spell
• etc., etc., etc.

Answer 2

Unfortunately point 1 doesn't adhere to the description of the spell; the very first sentence of Mirage Arcane reads:

You make terrain in an area up to 1 mile square look, sound, smell, and even feel like some other sort of terrain.

(Bold emphasis is my own)

You cannot make the illusory terrain look the same as before because the spell stipulates that you make the terrain "like some other" terrain, which is to say, not the same.

However, the same results you are looking for can be achieved without the need for Illusory Reality so long as your initial cast changes the terrain.

You can even dome them into a pit of lava that does damage as per the parameters of the spell and again, you need not use Illusory Reality.

The illusion includes audible, visual, tactile, and olfactory elements, so it can turn clear ground into difficult terrain (or vice versa) or otherwise impede movement through the area.

The illusion already has tactile elements that can impede movement; meaning you can reshape the terrain as you see fit and it can even do damage (which Illusory Reality cannot do). It doesn't even matter if they see through the illusion either!

Creatures with truesight can see through the illusion to the terrain’s true form; however, all other elements of the illusion remain, so while the creature is aware of the illusion’s presence, the creature can still physically interact with the illusion.

Essentially, it's even stronger than you originally thought but you can't do it in a subtle way.