I´m not sure if I understand the worlds in Might and Magic universe. Are most worlds fake worlds? Or I mean artificially created worlds? As far as I understand the ancients created most worlds either on board space ships as miniature worlds or the worlds are planet sized spacecrafts. I might completely misunderstand it, but could someone help me understand this? I think the only real planet is Terra. CRON, VARN and XEEN have been created by the ancients I think.

I think it is mostly real worlds, with a few artificials thrown in. Some of the worlds, like Enroth, are reached via spacecraft, and gateways connecting to the network are setup after that.

Huh. Was this new information revealed in HoMM 4+? (I pretty much stopped playing the series at 3 after I tried 4 and absolutely hated it.) If so, I'm kinda disappointed. :/ I prefer my fantasy and sci-fi to stay separate.

I really agree with you. I want it separate too, but no I don't think this is new information. You can see things like this in the very first Might and Magic game from 1986. Might and Magic and Heroes of Might and Magic takes place in the same universe. I mostly played HoMM 3 and I always thought it was just a plain fantasy game. That was until I started digging deeper into the lore. You have aliens, androids (for example Sheltem), spacecrafts and whatnot. Seems very strange to me, albeit unique I guess.

The first 3 HoMM games were pretty strictly Fantasy, while MM mixed in some sci fi starting from the very first game. The canon story of the two series started influencing each other around MM6, which picked up with story events that occurred after HoMM2.

As I understand it, the Armageddon's Blade expansion was going to include sci fi elements (results of the original canon ending of MM7), but fan revolts had them change the new faction to the Conflux.

Fans can be so revolting.
Instead of the Forge we got the ultra boring Elemental faction.

@JerseyFO, Bookwyrm: Wow, that's a real eye-opener! I never played the M&M games, but based on their cover art (some of which included stuff from the fantasy artwork great Larry Elmore himself), I'd have never suspected that there was sci-fi elements in them. In any case, I don't begrudge a series for mixing the two (even D&D did have some settings where there were hints of a technologically advanced race existing long before the current timeline), and it doesn't affect my enjoyment of the first three games. It does make me much less likely to ever try out the subsequent games in the series, but eh, that's what happens sometimes (like how the last Command & Conquer game was so different from its predecessors that it barely felt like the same game anymore.)

-MM1 presents itself as straight fantasy, but it is sub-named "The Secret of the Inner Sanctum" for a reason. :)

-MM2 was a story continuation from MM1.
-MM3 occurred on Terra. Terra is a real planet, but artificial worlds were pulled to it (or something; I'm not entirely sure).
-MM4 and 5 occur on the artificial world/plate of XEEN.

-MM6 is on a real world that was seeded by the Ancients, but it was one of the many that technologically regressed. If you've played all the way through it, then you are already aware of the Sci Fi elements.
-MM7 is on the same world as MM6, though a different continent. Again, Sci Fi elements show up near the end.
-MM8 has some sci fi elements, but they don't show up until the ending dungeon. Regardless, it shares the same world as MM6 and 7.

-I'm not familiar with MM9, so I don't know whether the Sci Fi is present. I seem to recall it was a different world/setting, though maybe it was a far distant corner of the same world?

-HoMM1-3 share the same world as MM6-8, though the HoMM games don't have the Sci Fi elements.
-HoMM4 keeps the same reality as HoMM1-3, but the 1-3 world is destroyed in 4's intro and 4 takes place on a new world. Again, the Sci Fi elements are not directly present.

-HoMM5 is a reboot, having entirely different lore. The sci fi is gone.

No sci-fi there. The setting is based more on Norse mythology.
The events in MM9, like HoMM4, take place in a new world where people escaped after the destruction of the old one. You meet at least one such person who escaped.
I believe it was initially meant to be same world as HoMM4, but later they switched to the Norse mythology setting, and since the series was abandoned anyway it was never resolved. You can assume it's a different world, or a different part of the same world as HoMM4.

Note that the expansions for HoMM4 are also disjointed. They could be taking place on same world or different worlds too.

This might be the document you want to read:
http://www.angelfire.com/ma3/neatpics/mmhistory.html

So the worlds are flat? People who believe in flat earth theory would be overjoyed to play this franchise :P Nevertheless, it is quite interesting. Thank you for posting this.