Can I turn a brightly lit area into an area of full darkness?

Unrelated, but are there any other spells that can produce darkness that can be seen through by creatures with darkvision?

One of the strongest spells in the game. Adamantine wall? Boom. Need lava? This does 6d10 fire damage without a save- and can be coupled with forced movement for more. But yeah adamantine walls are good.

Quote from Ylai >>

This seems to me to be Hallucinatory Terrain on steroids.  Keep in mind this not an Enchantment, Conjuration, Evocation, or Transmutation spell. It is an ILLUSION spell. It is designed to fool those who interact with it. There are differences, yes, but they are enhancements to Hallucinatory Terrain.

Additionally, the ONLY tag involved is the Control tag. There are no damage or other tags associated with the spell, therefore, the spell itself can not do damage. Given its size, I suspect it is designed to control troop movements. IMO, the defining statement is 

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.

There is no save. If the above statement means what I think it does, whether or not a creature identifies the terrain as illusory doesn't matter. Creatures with Truesight MAY choose to interact with the illusion as if it were real, all other MUSTinteract with it as if it were real. This is a major enhancement.

 Not having a damage tag doesn't mean it can't deal damage. Pretty sure the immovable rod has no damage tag but if you hit something then it's definitely gonna do something (probably counts as an improvised weapon, meaning a 1d4). Plus, being illusion doesnt mean it's only for fooling. The Illusory Dragon spell is made from "wisps of the shadowfell" which I'm pretty sure are actually there (they deal non-psychic damage, so they affect vulnerabilities, resistances and immunities. which points toward them being half real. Plus, the damage isn't completely ignored when you see it as an illusion). I'm not saying this spell makes real things, but just saying that Illusion spells aren't always just for fooling. 

demiplane + this so you can have a free vacation home

Quote from Joojins >>

demiplane + this so you can have a free vacation home

 Demiplane creates a demiplane, with a door accessing it. Getting out of one after the door has disappeared requires something else like banishment, plane shift or gate.

But yes, I ran both this and hallucinatory terrain on an illusionist, and they're *very* powerful with those subclass features. 😊

This is great for my Illusion wizard

And yet Crawford explicitly says it can hurt you. Bad. 

https://x.com/jeremyecrawford/status/988838034962436098

If you are thinking of the same tweet I linked above, he did what he often does in tweets- a general or partial answer :-).  He doesn't address the lava question, and the only specific "hurt" is drowning in an illusory lake.  So still not doing damage.  I've never had anyone drown in this scenario at my table before, but I'd allow it.  I'd also say usual swimming/underwater rule apply to this illusory water.

Okay, can you make a ten mile stone maze with this?
Of course not to hide anything within the maze, but rather to trap something in there or make a maze outside your wizard tower.
It isn't hiding, you can see the high tower still, but now you have to get through a maze to get there.
Even if this in not the chase, this is still a 10/10 spell, especially for every wizard that wants to make his land themed.

Even if the answer is no, you I think there is a 100% chance you can put a fake sword of legend there just to mess with people.