Humor, jokes, memes about TTRPGs
I once had a player that wanted a Decanter of Endless Water just to waterboard people ๐ณ
I think the screams would be muffled but still audible. Until the bag is closed, the extradimensional space inside is connected to the outside world. However, since sound can only escape from the opening and not the sides of the bag, I would rule that it is much quieter, granting disadvantage on checks to hear the scream.
It's up to the DM if it comes across like a portal to enter the bag or an impossible space like the TARDIS. Air does not flow between as you can suffocate and air would carry the sound, but I always rule it as feeling more like in impossibly large space rather than a magical portal.
I always interpreted the suffocation to be only while the bag is closed. It doesn't make much sense if physical objects can enter the bag but not air. Why not?
Creating the bag would create a very big underpressure, immediately imploding the bag and probably killing the creator
You could just kill the guard by leaving them in the bag
I would immediately shift your alignment to chaotic evil for it because you're literally making them suffocate to death over a period of about ten minutes, but it's still RAW.