If the target is native to a different plane of existence than the one you're on, the target is banished with a faint popping noise, returning to its home plane. If the spell ends before 1 minute has passed, the target reappears in the space it left or in the nearest unoccupied space if that space is occupied. Otherwise, the target doesn't return.

Does this mean if I cast this on a creature that is from the mortal world or whatever they will reappear?

Yeah, I think so.  It's good for high cr otherworlders, but on things like undead, not as good.  Unless it's a lich of course.

I was reviewing abjuration.  The description says 'members of this school are sought when baleful spirits require exorcism'.  This led me to wonder if spirits/ghosts are still native to the material plane, or if they become native to the astral plane after they become spirits/ghosts? I was wondering because I am not certain if a banished ghost would return after a minute or not.

Any insight you can offer me?

All undead go to Shadowfell when banished, so it works on them, too.

Additionally - it works on anything from material plane IF you're casting it while on another plane. So for example: If there's two humans (each native to material plane) and one casts banishment on the other, while they're on a plane of fire, the banished human would go back to material plane and - after 1 full minute - wouldn't come back.

 If you're on a plane of existence that you are not mayben to can you cast banishment on yourself to return home?

Quote from ImmortalWitness >>

 If you're on a plane of existence that you are not mayben to can you cast banishment on yourself to return home?

 
Based on the way I've seen Jeremy Crawford make rulings, I believe that to be true. You'd end up back at your home plane and, provided nothing stops you from concentrating for the full minute, you'd be back permanently. But I also note that the spell doesn't specify an arrival location, so the DM could rule that you arrive somewhere on your home plane far from the place you left it. Oh, the adventure possibilities!

Unfortunately Banishment also incapacitates the target while they're banished, and being incapacitated causes you to instantly lose concentration ^^'

D'oh! You're right, of course. Scratch everything I said!

Quote from KaptainKittens >>

Unfortunately Banishment also incapacitates the target while they're banished, and being incapacitated causes you to instantly lose concentration ^^'

 I don't think that's true.

If the target is native to the plane of existence you're on, you banish the target to a harmless demiplane. While there, the target is incapacitated.

They're only incapacitated while in the harmless demiplane, and that only applies if the creature is native to the current plane. It doesn't say anything about non-native creatures being banished to their home plane being incapacitated.

Super late reply but

”f the target is native to the plane of existence you're on, you banish the target to a harmless demiplane. While there, the target is incapacitated. The target remains there until the spell ends, at which point the target reappears in the space it left or in the nearest unoccupied space if that space is occupied.”

if they’re native to the material plane and you’re on the material plane they’re banished to the demiplane.

Quote from pkmnfrk >>

Quote from KaptainKittens >>

Unfortunately Banishment also incapacitates the target while they're banished, and being incapacitated causes you to instantly lose concentration ^^'

 I don't think that's true.

If the target is native to the plane of existence you're on, you banish the target to a harmless demiplane. While there, the target is incapacitated.

They're only incapacitated while in the harmless demiplane, and that only applies if the creature is native to the current plane. It doesn't say anything about non-native creatures being banished to their home plane being incapacitated.

 I agree. The two separate clauses for native and non-native planes describe different results for each. 

Quote from Ziveron >>

Quote from ImmortalWitness >>

 If you're on a plane of existence that you are not mayben to can you cast banishment on yourself to return home?

 
Based on the way I've seen Jeremy Crawford make rulings, I believe that to be true. You'd end up back at your home plane and, provided nothing stops you from concentrating for the full minute, you'd be back permanently. But I also note that the spell doesn't specify an arrival location, so the DM could rule that you arrive somewhere on your home plane far from the place you left it. Oh, the adventure possibilities!

 

 I like the cut of your jib and would like to subscribe to your newsletter, goodsir. Also, this is just good clean fun. 

Ah, I have to agree with you on that. I didn't consider the 2 scenarios separately, my bad! Thank you for clarifying :)

Quote from Holvr >>

All undead go to Shadowfell when banished, so it works on them, too.

What's your source on that? AFAIK, there are undead creatures native to the Shadowfell, but not all undead are native to there. And there are many kinds of undead. Some undead creatures are also demons and therefore native to the Abyss. An atropal is an undead titan native to the Astral Sea. Undead is more of a quality of a creature than a race of creatures. 

Quote from Daien_lll >>

If the target is native to a different plane of existence than the one you're on, the target is banished with a faint popping noise, returning to its home plane. If the spell ends before 1 minute has passed, the target reappears in the space it left or in the nearest unoccupied space if that space is occupied. Otherwise, the target doesn't return.

 

Does this mean if I cast this on a creature that is from the mortal world or whatever they will reappear?

 Yes, but only if you are on that same plane (the mortal world) when you cast it. This is described explicitly in the first part of the spell (emphasis mine):

"If the target is native to the plane of existence you're on, you banish the target to a harmless demiplane. While there, the target is incapacitated. The target remains there until the spell ends, at which point the target reappears in the space it left or in the nearest unoccupied space if that space is occupied." 

It's important to note that it depends where you are when you cast if. If you and your target are both in the Astral Sea, and your target is from the Prime Material Plane, it will not come back after one minute, because it is not native to the plane of existence you're on.

I'm a little surprised this spell isn't part of the Druid spell list. 

Most descriptions of Druids I've seen involve something about being 'defenders of the natural world' but they don't get to use a really useful spell for sending extra-planer beings back where they belong?

you cannot cast banishment on yourself

Why not? As long as you're a creature you can see it should work. Heck you can even choose to fail the saving throw.

You can yes. Then you'd become incapacitated, lose concentration and reappear.

Hm, I see your point but you're only incapacitated if you're native to the plane you're currently on. So I'd argue it's possible if you"re not on your home plane. As others have pointed out, it doesn't specify where on the target's home plane they're banished too so it's not perfect.

I can definitely see a cool case for a tiefling wizard casting it on themself and appearing somewhere in the Nine Hells because their backstory says they were born there.

All of that talk about "Could you cast this on yourself to return to the material plane?"

I would say the answer is yes, unless you're on Carceri.