Millennium Wars

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Having temporary control of the Event Synthesizer and therefore over reality itself, the demon Melanicus instigated, for no other reason than to do it, the Millennium Wars, encompassing a thousand different worlds and a thousand different time periods.

The worlds ruined by the Wars included a future Earth. (COMIC: The Tides of Time)

The Fourth Doctor was briefly caught in one of these conflicts, not understanding its significance. (COMIC: The Deal)