I just had an idea for a campaign, a necron incursion has all but smashed hive world Fendora. If it is not stopped here and now the Machine xenos will rise a pose a new threat to the crusade. The kill team is all that can be spared. The PDF and Imperial guard forces stationed there are shattered, the only resistance is an underground movement that is holding the xenos at bay, but they are scattered and under supplied. The kill team must drop into enemy territory with no backup and no idea what to expect. They drop on a ruined world, Reports said it had been only 2 weeks, but it seems to have been years. They must find elements of the resistance and decide what to do from that point on.

I think the idea of a raven guard style behind enemy lines fight would be cool, it could last weeks to years of narrative time as the kill team links up with different fighters who have no real leadership and proceed along different paths, all the while avioding necron patrols and xenos kill teams.

Got the idea from the terminator future scenario.