Yair said:
The thing is, there would be a large discontinuity gap unless you use Midnight rules anyways. Magic works differently, that is the major change.
Since I don't think the Midnight rules are that great anyways, and they definitely don't represent a D&D world that has fallen, I'm thinking of using another system altogether.
I ran a brief (6-7 session) Midnight campaign a few months ago, but I simply used the standard D&D rules for the most part. It’s not that I dislike the Midnight classes & spellcasting rules, but I didn’t find them interesting or different enough to go through the trouble of converting all my players over. I did make use of the modified Midnight races, because of the setting specific flavor they provided, but I stuck with the standard D&D classes and magic system. I simply disallowed Clerics, Paladins, and any other deity dependant classes. At first, I restricted other full-fledged spell casters (druids and wizards) to no more than half your total character level, so you could be a druid 3/ fighter 3, but not a druid 6. After the first couple of sessions, however, I decided to lift that restriction and simply use the threat of overwhelming, unavoidable hunting forces to limit the amount of flashy magic that was used.
For a dash of extra flavor, I also allowed psionics at the request of a couple of my players. I treated it as a new discipline only discovered and developed in secret within the last generation. It was a power that the Dark Lord was not yet aware of, and could not detect or track. The plan was to have him eventually discover the existence of psionics, probably through the actions of the PCs, and to quickly mount a concentrated effort to root out and destroy all psychics, using hunting squads of red crystal psion-killers.
In any case, the campaign worked really well and the players seemed to have a lot of fun. We only ended it early because of increasing time demands outside of the game due to jobs and such.
Using the standard D&D rules also makes it much easier to do the “prequel” type approach, where one generation of heroes fails to stop the rise of the shadow, and then fast forward 100 years to start a new campaign under the oppression of the Dark Lord.