Voord invasion of Marinus

The Voord invasion of Marinus (PROSE: Doctor Who and the Keys of Marinus) occurred when Yartek led the Voord to assault Arbitan in his Great City and take control of the Conscience of Marinus. (TV: The Keys of Marinus)

At 701 zeniths precisely (Inter Galactic Time), three BXV sub-oceanic assault craft penetrated Marinian territorial waters at a depth of fifty sonars, fitted with antimetradar devices to remain undetected to within one hundred yards of the shore before surfacing and landing on the beach near the Great City. (PROSE: Doctor Who and the Keys of Marinus)

Eventually the Conscinece of Marinus was destroyed when Yartek activated it using a false key. (TV: The Keys of Marinus) Several hundred Voord were forced off-world by the Arbitans, and millions of years later, the Voord still planned to return and seek revenge on them. (PROSE: The Fishmen of Kandalinga)