Ah, Gem Golems are puppeted by specific mages ("golem masters"), so that's a no.
:) There wouldn't be anything wrong with two living characters, though, like a Siren and a Praetorian who protects her.
EDIT: Ninja'd. It still doesn't fit, Kilt. Not the Golem, anyway. A master and her Golem would be a little different, but not a Siren and a lone Golem.
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As for Nightingale... I don't know, enigma. I'm going to need a more in-depth description of dreamwalking, for one, and for there to be some sort of defense. I like it, as a Luna-aligned power, something that Nightmares would do, but as its described I think it needs more limits (especially for a girl who never completely went through the induction). Honestly, the background is also pretty weak. Come up with more development, other people that she has interacted with or who had an effect on her. Just something more. At the moment she's rather bland.
Alternatively, shoot me a PM with an IC sample, and we can do it that way.
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:) Derp, be sure to add in some strong willpower. No average pony would be able to simply get sad and run away from the Cult. Will the character have any combat experience, or magic or anything?