Alright, so personally I don't know much about them. But after asking Karve for assistance he managed, despite being utterly wasted (his words, not mine :P), to gather the following sources for you:

Book of Circles.Sword-Wisdom of Master Saikhalar. Memory Stone of Makela Leki.

Sword-Wisdom of Master Saikhalar.

Memory Stone of Makela Leki.

Furthermore, anything about Hunding, the walkabout and the worship of Onsi and Leki should help you as well.

Again, you have our resident Lorc to thank for these, so if you have any further questions don't hesitate to ask him.

[blockquote][b][url=/profile/Relycs]Relycs[/url] said:[/b]

Is there any way to safe souls that are captured in soul gems? Like if someone is going to die and you put his soul into a gem to keep it from disappearing, is there a way to sort of safe or do something for it? Or does it not matter because it would be the same as if the creature would die? The body is dead at that point btw. I remember that the guy from the Azura's Star quest couldn't be safed because he was too long in there or whatever, but what if it happens in a relatively short amount of time?

Thanks in advance.

[/blockquote]

You save the soul gem. Souls only go to the Soul Cairn when they're "spent" via enchanting or recharging.

The Azura's Star that Malyn used was a unique circumstance. The Star was broken due to containing Malyn's soul which may mean that it couldn't be used for enchanting and we had to "clear it out". It could also be that Malyn used some sort of spell on the Star that as long as his soul was inside it it couldn't be used, which is what the quest seems to imply.

[blockquote][b][url=/profile/Relycs]Relycs[/url] said:[/b]

@Ebonslayer: But there is nothing to do with the gem else than powering something? No moral / "good" thing do do?

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There's little else to do with a soul gem but use it. I guess you could use it as a decoration but I doubt that'd be "honoring" much and a black soul gem is a bad thing to keep on display, people might think you're a necromancer. You can possibly donate it to Falion or someone else who can attempt the ritual to cure vampires but I'm not sure what happens to the Soul inside, from what Falion says during the ritual it sounds he's giving it to a daedra.

[blockquote][b][url=/profile/Relycs]Relycs[/url] said:[/b] @Ebonslayer: But there is nothing to do with the gem else than powering something? No moral / "good" thing do do?[/blockquote]

[blockquote][b][url=/profile/Relycs]Relycs[/url] said:[/b] Ah well that's too bad. Thank you for the reply.[/blockquote]

Another "good" option might be to place the filled soul gem at the shrine of one of the Divines, perhaps choosing the Divine that the person may have worshipped in life.

[blockquote][b][url=/profile/Relycs]Relycs[/url] said:[/b]

But isn't that like keeping the soul trapped there? Do souls "want" to go to their respective realm/etc?

[/blockquote]

Their soul is trapped in a soul gem. They aren't going to their preferred afterlife whether they like it or not. After getting soul trapped you have two options, one is to stay in there in eternity as a prisoner, or have it be used and you're sent to the Soul Cairn as a slave. Either way, not a good outcome for the poor soul in there.