I have the 1.7 version from GOG.com.
I'm on mission 5 of the campaign ("fear"/Elmshadow), and no minions ever come trough the portal. I keep getting attacked, but all I have are imps. Finding the jail doesn't seem to trigger any, either.
All of the guides I've looked at for this mission seem to assume you get minions as normal. I've sat around with a lair, hatchery, and training room built until the enemies tunnel into my dungeon, but still nothing.
Am I doing something wrong, is this a bug, or working as designed?