Pulling player records
The two parts to the UNION have too much in common.  I believe this query is equivalent to yours.

SELECT ID, XAxis, YAxis, Player, Castle, Alliance
    FROM SC75
    WHERE
        Snap = (SELECT MAX(SavedSnap) FROM DataSnap WHERE Server = 75)
            AND
        (
            (hex(Player) IN (hex('Vandiel'))
                OR
            Player IN
            (
                SELECT AF.Alts
                    FROM AltFiller AS AF
                    WHERE hex(AF.Player) IN (hex('Vandiel'))
            )
        )
    ORDER BY Player, Castle;