Superb Song of the Valkyries: Symphogear

From the Horizon of Mankind's History (5x1)

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Going off of data retrieved from Tiki's remains, the Symphogear users head to Antarctica, where they are confronted by a powerful automated "coffin" that Adam was investigating. Despite the overwhelming odds, Hibiki and the others manage to destroy the coffin, inside of which they find the corpse of a Custodian.