Something I always thought about, was an MMO that had a fairly realistic day and night cycle. What I mean by realistic is one set on an actual 24 hour day and night. One in which a player can enter an area during the day and find a completely different set of obstacles. For example you could have a mob or boss that only comes out at night such as a vampire. During the day if you were to go to that location there would be minions of the vampire or you could even find a weekend version of the vampire boss. Assuming the vampires and secret world have those sorts of weaknesses.
Creatures such as werewolves also traditionally operate at night, and this adds the ability to have to realistic moon cycle, So during the day when you go to this werewolf's house, he may be in human form and needs to shooting you with a gun. The trick to these encounters is that the mobs minions or traps could easily be harder to do than the boss itself it's just a different set up.
There is only a couple problems that I can think of with this plan.
1: If it's a real life 24 hour day, the problem occurs where and the players game time is limited to a certain time of day. so he/she can only play during the day they may miss specific lutes or encounters that only happens during the night. This could possibly be solved by making a two for one exchange. So one real life hours 2:00 PM game hours. It's not realistic but close.
2: the tendency to use the same at for a different adventure. So it's true that you're going to be attacking the vampires same house during the day than you would be at night, but you could change the chateau range of room windows could have light coming to them during the day that they don't turn the night so you would technically easy have to make of the same map twice.
3: spawn campaign; if you know the vampire only comes out at night and tonight cycles the same for everybody everywhere. Then you're going to have a lot more people come in detail the vampire at that time of day or night technically. This can be solved instances or dungeons that only people with the proper costs can go into. Doesn't really work was a sand box type area.
what do youall think of this?