A couple of hopefully helpful things.
1. Which flavor of Elezen?
Just Ishgardian is fine, Ishgardian Elezen don't seem to care about the split too much. Gridania on the other hand is pretty intolerant to outsiders and pretty prejudiced toward Duskies. There is an angle there to be worked that could aid in the transition if your character has some traits that are outside the normal outsider in Grid. Bad things as a result of this can chain you into...
2. What made your character snap?
A common thread for the DRKs we can observe is that some event/injustice/tragedy. Usually the event is accepted as "OK" from the viewpoint of the society they are living in (fortunately Gridania is a terrible terrible place). This caused them to break a bit mentally and emotionally. The result of the break being the point at which they started accessing their Darkside. While it does not necessarily need to be as dramatic of a break and result as the one DRK quest line (omitting specifics because SPOILERS), something gets them to the point that they decide to correct society's wrongs (with darkness and a great sword!). This can lead you tooooo...
3. What emotion drives your character's Darkside?
DRK and Darkside stuff flows from emotion, and not just the "dark" ones. There is an emotional core that fuels DRKs and their stuff. Fury, sorrow, and pain are some obvious choices, but so are joy and love. Anything emotion is valid, the field is wide open. The response and handling of that emotion is what really counts. It is even possible to have this "core emotion" be an unknown aspect to the character (or even one they are unwilling to admit to themselves). It does not necessarily need to be the direct, raw, and visceral emotional response to the event in #2. Depending on the story you wish to tell that initial response to event-o-breaking fun can even be something that is holding them back as they develop and grow.
I hope this has been useful. Feel free to poke me if you have other questions or need some stuff clarified.
1. Which flavor of Elezen?
Just Ishgardian is fine, Ishgardian Elezen don't seem to care about the split too much. Gridania on the other hand is pretty intolerant to outsiders and pretty prejudiced toward Duskies. There is an angle there to be worked that could aid in the transition if your character has some traits that are outside the normal outsider in Grid. Bad things as a result of this can chain you into...
2. What made your character snap?
A common thread for the DRKs we can observe is that some event/injustice/tragedy. Usually the event is accepted as "OK" from the viewpoint of the society they are living in (fortunately Gridania is a terrible terrible place). This caused them to break a bit mentally and emotionally. The result of the break being the point at which they started accessing their Darkside. While it does not necessarily need to be as dramatic of a break and result as the one DRK quest line (omitting specifics because SPOILERS), something gets them to the point that they decide to correct society's wrongs (with darkness and a great sword!). This can lead you tooooo...
3. What emotion drives your character's Darkside?
DRK and Darkside stuff flows from emotion, and not just the "dark" ones. There is an emotional core that fuels DRKs and their stuff. Fury, sorrow, and pain are some obvious choices, but so are joy and love. Anything emotion is valid, the field is wide open. The response and handling of that emotion is what really counts. It is even possible to have this "core emotion" be an unknown aspect to the character (or even one they are unwilling to admit to themselves). It does not necessarily need to be the direct, raw, and visceral emotional response to the event in #2. Depending on the story you wish to tell that initial response to event-o-breaking fun can even be something that is holding them back as they develop and grow.
I hope this has been useful. Feel free to poke me if you have other questions or need some stuff clarified.