If you have gained control of a creature with mark of the oni and you have no demons Mark of the Oni is sacrificed. Do you then lose control of creature that you gained control of with the spell?
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Yes; Mark of the Oni's ability "You control enchanted creature" is a static ability that works only while Mark of the Oni is on the battlefield and attached to something (C.R. 611.3b, 113.6, 303.4m, 604.1).
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