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Even though the texts of The Song of Ice and Fire series do not confirm whether or not the various gods exist, there are certainly many magical acts claimed on their behalf by their adherents. The gods of Essos very clearly have acts claimed by their adherents, and the Old Gods are seen as active in the north (though I'm not sure if it's explicitly stated that they are responsible for the skinchangers.)
Does the series ever present any magical acts as being caused by The Seven?
And though the Ironborn gods are nowhere near as prominent, the same can be asked for them: are any magical acts claimed to be their work?