I don't really think it needs an "exterior." A deity's symbol doesn't have to be like a flag, with a background or whatever. Think of the Christian cross, or the red crescent used by Islam.
I'd just go with the red scythe outline--it'd be the kind of thing that a priest could have embroidered on his robes or carved into an altar. If you don't think the scythe outline is elaborate enough, or that it needs to be more stylized, think of a way to do that. <p>
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