@Jarkes  
it being a killing curse took away from the impact him falling through the veil had when I read the books. it’s like beheading a corpse. not to mention that the killing curse is instantaneous in every instance aside from this one.

@hawthornbunny  
well, in the book and the movie it’s a bit ambiguous as to where it leads exactly, but it’s quite clearly a gateway to SOMEWHERE and wherever it goes people can’t seem to return. I personally headcanon that it merely leads to other universes, but changes the universe it transports to quickly so that the portal closes pretty much the instant you’ve passed through it. I’ve been wanting to write a sirius black in equestria fanfic for a few years now.

@Fwelin  
I remember reading - not sure whether in the book itself or an alternate source - that the amphitheater looked even older than the rest of the Department of Mysteries. Which gave me the impression that the Dpt. of Mysteries, and then the Ministry, were founded around that portal in order to investigate it.

@hawthornbunny  
The room it was in also had bench like seating around it, with it in the middle. The implication was that it was used in some kind of spectacle, such as executions.

@runesorcerer  
@Jarkes
 
Yeah, the way I understood it was that it was a gateway to the world of the dead (Luna alludes to this at the end of the book). One of the core themes of the Harry Potter series is that death is immutable; you can’t cheat it, you can’t stop it, and you can’t come back from it. That’s why I think the book deliberately leaves the nature of the spell that hit Sirius ambiguous; because it doesn’t matter. Whether it was a stunning spell or a killing curse, if it pushed him through the gateway, he’s dead either way.
 
As for why the gateway is there at all: it’s the Department of Mysteries, and death is the last great mystery.

@Senpai Wrench  
Who cares?  
The (Original) Harry Potter series has been done for a couple years.  
If you aren’t caught up, you likely haven’t seen any of them.  
Like me.

@Jarkes  
As far as I remember, the veil is a one-way portal to the world of the dead. It wasn’t clear what spell hit Sirius, but it was clear that he crossed the veil to never come back. It’s not that the veil killed him, it’s the fact that he crossed that portal to never come back.
 
And in some way, it killed him, yes. I think Nearly Headless Nick explains it later, but not clearly enough to fully understand it.

This scene actually made a lot more sense in the film than it did in the book. In the book this void thing (whatever the hell it’s supposed to be) was described as nothing more than a simple black curtain that appeared to have absolutely nothing behind it, which never really made a whole lot of sense to me. Plus, in the book, it wasn’t made clear what spell Sirius got hit by that knocked him in there. Here, he was unambiguously hit by Avada Kedavre, and fell into something that actually felt like a void.

Oh my, did I create a meme? This can’t end well. XD

D: why would you do that??!

@Mr. Bait  
you’re sirius-ly the worst.

I’m waiting patiently for Dumbledore.
 
Should I have spoiler tagged that?

Shirley you can’t be Sirius!

Oh no, please say this isn’t going to become a thing.

Hey, this is no joking matter. This is sirius business.