I wanted to tackle this part first, because I think it’s crucial to the concept we’re working off of here. (Nice story impetus, by the way, Jeff!) Corruption and greed, though they come in many forms, require no technology or magical powers to make themselves known. So, naturally, bad guys will show up on both sides and the only question they pose is 'how much power do they have over the story?'
As far as a motivator for the SF side, however, this strikes me as a good reason for their outreach. If we have within the SF framework a good side and an evil side, both trying to make contact/dominate the Fantasy side, it provides a lot of options for alliances, betrayals, and plot constructs. The question for me is: who makes contact with the Fantasy side first, good or evil?
Personally, I think the evil side should make overt contact with the right people, disguised as nice, helpful folks, while the good side sends one or two deeply noble characters who have to work their way from the lowest dregs of society to make contact with the right people. But I’m open to suggestions.
In Him, Lex
Lex[br][br]~Oh Lord, keep your arm around my shoulder and your hand over my mouth.~
Perhaps the noble ones are an underground-type in the sci-fi society? Then maybe they would have to blend and stay hidden within the fantasy world in order to avoid contact with the bad characters? Perhaps the fantasy world characters are more suspicious of them than the outwardly good but in reality bad contacts?