It honestly seems like if you get both shaders before shells you never get a shell at least that's how it seems to me cuz I have yet to get a shell and I have both shaders on all 3 of my characters
English
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I got both shaders in my first two games and then nothing until yesterday I got two of those chocolate ghosts but only at 314...everything else has been blue gear or motes
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Got all four [2 shade then two ghosts] in 3 hours
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Just bad luck for me then I guess