As a DM how do you combine Sci Fi and Fantasy?

[haakon1]

I used (and would recommend) Stargate d20 with 3.5 edition D&D.

It's nearly compatible. I created some of my own classes for this to get the PC rules slightly closer to 3.5e, but I'm not sure that was needed.

As to the comment about not pulling the rug out from under the PC's by having them make sci-fi characters and giving them a D&D setting, the approach I took was to be upfront about it, during character creation. Sure, they are more likely to be carrying extra batteries and ammo when the change happens, but it's not like that's a bad thing!

 

[scourger]

I've tried to get the sci-fi chocolate in the fantasy peanut butter a few times, and it generally doesn't work. I also made 2 replies to this thread 2 days ago but both got lost somehow. So, here (hopefully) is a condensed version.

First, decide what kind of game you want to run and find out what your players will play. It sounds like you have the crash basis, but what is the story goal? Just being stranded is no fun, unless they are duty bound to bring the war to the savages (like 40K). I suggest that the goal be that they are trying to either repair the ship or fix the comms. Either way, they seek rare materials so they can get off planet. Then, when the time comes, they have the interesting choice of either leaving or staying behind forever in the backwater where they have made new friends, or are rulers, or whatever motivates them.

Next, decide what character options are open to them. I suggest that the high tech PCs be restricted from taking any spellcasting classes. Ultimately, it doesn't really matter if you use the PHB non-spellcasting classes or sci-fi classes from other sources. I like the explorer from Omega World d20. The idea is that the PCs are different because of their mastery of technology, which should be fairly robust against magical effects. If the PCs don't have spells, you can really trim the fantasy foes to the bare essentials, like DDM stats, and just run the game for the fun story. That's what I would do. Plus, you can sprinkle in some Star Wars minis if you want to.

Last, decide how the story will end. For instance, at what point will they have the choice to leave the planet? Presumably, they will have conquered many foes and gathered the rare materials they need. But, they at last have to choose to stay or go. I think a campaign story should have an end, though. If you want to continue the game, have another generation come back; possibly reuniting with descendants left behind. That would be a cool twist.

As a post script, consider using Savage Worlds. That game system is much better suited to this type of genre-mixing.