I also RP a non-Ishgardian dark knight. My character's soul crystal was given to him by another player-character, who I think was given it by an Ishgardian dark knight. I find it really funny that the Rogues' Guild quest chain and the Dark Knight quest chain were written by the same writer, because they both follow the same "justice in the darkness" trope, haha...
Ah... to answer something in the OP I didn't throw my 2p in on yet...
I think "darksides" are highly personal (based around the person, their experiences, the experiences held within the specific soul crystal they own, and how they would expect or want such a thing to manifest), and so I think... how you choose to present/shape it is down to you, and what makes sense for your character...
As long as it has the same drawbacks as it should, i.e. that it's possible to give onesself over to it too much and cause onesself harm. Remember that at its core, no matter how your character perceives it or describes it to other people, it's an ability that feeds on your character's inner aether to provide strength.
My character's Darkside did "take a face/voice", superficially similarly to how Esteem took Fray's, but that's because his predecessor told him to expect it to. It doesn't pull the wool over his eyes in quite the same way Esteem did the Warrior of Light, because my character has an actual real physical mentor to advise him on what it is and what it can (and can't) do. Its apparent "behaviour" is heavily informed/guided by how my character expects it to behave, based on what his mentor has told him and what he expects out of the person whose voice it mimics.
If my character's mentor had told my character to expect it to be a feeling in the back of his mind, then it probably would've manifested like that instead. IDK, I think all we can know from canon thus far is that it's highly variable based on circumstance - I try to inform my writing of it in equal parts by what the quests were like, what little I've seen of how other players play the job, and what I think works best for my character and the role I want his soul crystal to play in his overall story.
Ah... to answer something in the OP I didn't throw my 2p in on yet...
I think "darksides" are highly personal (based around the person, their experiences, the experiences held within the specific soul crystal they own, and how they would expect or want such a thing to manifest), and so I think... how you choose to present/shape it is down to you, and what makes sense for your character...
As long as it has the same drawbacks as it should, i.e. that it's possible to give onesself over to it too much and cause onesself harm. Remember that at its core, no matter how your character perceives it or describes it to other people, it's an ability that feeds on your character's inner aether to provide strength.
My character's Darkside did "take a face/voice", superficially similarly to how Esteem took Fray's, but that's because his predecessor told him to expect it to. It doesn't pull the wool over his eyes in quite the same way Esteem did the Warrior of Light, because my character has an actual real physical mentor to advise him on what it is and what it can (and can't) do. Its apparent "behaviour" is heavily informed/guided by how my character expects it to behave, based on what his mentor has told him and what he expects out of the person whose voice it mimics.
If my character's mentor had told my character to expect it to be a feeling in the back of his mind, then it probably would've manifested like that instead. IDK, I think all we can know from canon thus far is that it's highly variable based on circumstance - I try to inform my writing of it in equal parts by what the quests were like, what little I've seen of how other players play the job, and what I think works best for my character and the role I want his soul crystal to play in his overall story.