Very much this. It even feels very "rogueish" to employ that strategy and it’s far from broken, so I don’t see why you would ban it.

Get's transported to a time where all Sphinxes have died.

I know it’s a joke, but I'd say "mostly dead" is just when you roll death saves.

As I have said in another comment, that is RAW not what would happen:

"You can’t even cast it on something behind the wall, because you cannot target something (or someone) with a spell if they are behind total cover. Total cover is created by being behind completely behind an obstacle (like a wall). This counts even if the obstacle is invisible."

Furthermore, because if you chose an invalid target for a spell, you’d still expend the spellslot but there would be no effect. So you actually spend a sixth level spell a lot to achieve nothing."

It’s very much not RAI I'd say and I would likely handle exactly like you described, but the RAW was so wonky that I wanted to make the meme when I found out about it.

No. If we assume that you have to target the wall it would at the very least stop after destroying the wall.

But by RAW, you can’t even cast it on something behind the wall, because you cannot target something (or someone) with a spell if they are behind total cover. Total cover is created by being completely behind an obstacle (like a wall). This counts even if the obstacle is invisible.

Furthermore, if you chose an invalid target for a spell, you still expend the spellslot but there will be no effect. So you'd actually spend a sixth level spell a lot to achieve nothing.

I would not recommend doing it this way, but that’s what the rules say.

Oh definitely. I assume that RAI this is the intention.

Probably. An author once wrote this piece of conversation:

"Wait? You can transform matter. Thats magic." "Your people can use metal to fly over buildings." "Of course they can. It makes perfect sense."

Having a world, where "magic" actually exist raises a lot of questions about some conventional expressions and cultural aspects.

"So what do you have? "

"A sword!"

"A sword?"

"Yes. And I can hit with it twice as often twice every hour."

"... I'll stick to my spellslots thank you."

"... It sounded better in my head."

Never show this to my players please.

Something tells me that this will be the favorite picture of many people… I am not among them of course.

As long as the players got to watch and listen, as the two lovebirds did there thing, there would be no reason to complain. You don’t get to see a a high quality romantic comedy show every day.

What would Konsi do should they have a serious fight? Throw her out?