Night effect? I suppose you don't mean removing/ changing ownership of everything that belongs to player 1, so that the fog of war covers an area. If your scenario is for multiplayer, and if all players are active, I'm afraid that back-into-fog thing is all you can do. A complete night effect requires passive dummy players and constantly changing diplomacy.
Here is how a complete night effect works. You can cover visible areas in complete darkness again if you haven't explored it yourself, and if you are only seeing it through an ally's LOS. The ally could have a house, a flag, a torch or a shipwreck (works only in AoK, has no LOS in AoK:TC) as a 'map revealer' in that area.
Try to mess with cartography and diplomatic settings: Have a trigger change your diplomatic setting to an allied 'LOS-Giver' to neutral or enemy (don't make that ally change his setting, or your'll get those annoying diplomatic messages), and the lit up area will completely fall back into darkness again. To prevent players from messing with the diplomatic settings, have looping triggers fix the settings. Deactivate those looping triggers only just before the settings are supposed to change.
Things to watch out for if you use that method:
a) That LOS-Giver shouldn't have any objects near your units, or your band of guys will suddenly attack that peaceful village they're resting in.
b) If you research cartography, all allies will be visible on the map. If you want to prevent that and have an "allied" village which is undiscovered, give that other village the diplomatic stance neutral or enemy towards you - but deprive them of anything that can shoot, slash or poke at you, or you'll have a very unfriendly ally! If you do give them any military stuff, make sure you freeze all of it with an area effect. "Freeze" also works for towers and castles to some extent.
Ingo