Souls stone
So, to get the stone you have to give away a soul.
But ... when you return the stone shouldn't you get back that soul?
it's, literally said in the movie, "soul for soul".
So, to get the stone you have to give away a soul.No deposit and NO refunds.
But ... when you return the stone shouldn't you get back that soul?
it's, literally said in the movie, "soul for soul".
But seriously, when this trade is made the details of the contract are told to you explicitly and they are not just a "Soul for a Soul".
The Red Skull first explains who or what you are dealing with, "The Stone has a certain Wisdom", which would imply that you are negotiating with some type of sentient entity which is either the Stone itself or some other power overseeing the stone. This is not made exactly clear but let's go with the Soul Stone being sentient and in this case aware. The Red Skull also explains that what Gamora and Thanos are looking at is "The Price". The cliff is like an altar to which a "Sacrifice must be paid".
The Red Skull explains the next part of the contract or bargain, "The Stone demands a Sacrifice. Thanos being the inquisitive but impatient Titan that he is, quickly responds with a "What?".
The Red Skull further explains the remaining three part detail, "1. In order to take the Soul Stone" and 2. "You must lose that which you love", finally 3. "A Soul for a Soul".
The Sacrifice is demanded to be paid and is required even before you can take possession of the Soul Stone. The "Sacrifice" is done in this case through a death. The death can not be undone otherwise there was no sacrifice. The Soul Stone does not need to give up a Soul or make a bargain for a soul in order to regain possession of itself as it is and always will be the Soul Stone. The contract is a one-way bargain.
Here is a wrinkle not explained. Now that the Soul Stone is in the possession of an owner there must no longer be a need for a "Keeper". The Red Skull should be free of his burden and tasks.
Another wrinkle: If Thanos had never been killed, nor had he destroyed all of the stones with the stones, and let's say he died. Would the Soul Stone find it's way back to Vormir? Would the certain kind of wisdom of the Soul Stone still be in place and would the Red Skull or maybe even Thanos be imprisoned on Vormir serving the role as the Keeper, as Thanos would have been the last person (or Soul) to use the Soul Stone?
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Here is another wrinkle: Hawk was the new owner of soul stone, just like Thanos, how could anyone else be able to use it? They did not make the sacrifice.
Also Aether (reality stone) was not in form of a red stone, it was a liquid life from, who turned it into a stone? I can understand Thanos has enough resources to do that, Asgard probably did not. When they took it from Asgard, it was still in liquid form. Who and how did avengers turn that into a stone?
There does not appear to be any limitation on who can or cannot use the Soul Stone once it has been acquired from Vormir (Vormir was setup as some type of altar for the sacrifice of course.), and in addition the general proximity of the Stones all within the Guantlet seems that they are made to work in unison where one is augmenting the other or the wearer has some willfully enhanced control because of the Stones and the gauntlet.
I believe that Thor, in Thor The Dark World, attempted to destroy the Aether and discovered he could cause the Aether to transform with Mjolnir. Remember the Aether is extracted rom Jane in one form and subsequently converted to a Stone or Ingot to be used in the Guantlet. It would appear that the reverse was possible also for re-transforming the Aether.
Just my thoughts.
At least that is what appears in movies, I don't know much about the soul stone to agree or disagree with you. But if it can be used by others then that means soul stone once acquired is not going back. That implies that is the first time since the beginning of universe soul stone is acquired, that is a bit hard to believe. If, as you have asked, the owner's death would send it back then Hawk's death if happened could end the whole battle in the end.
About aether, in movies Malekith directly extract and absorbed aether. Mjolnir did make aether solidify into many crystal fragments, but it returned quickly back into liquid form. Mjolnir's effect is not permanent, also not into one stone. So I don't think that was a practical way to turn aether into reality stone.