A random Druid instead of Gem in the campaign.

I played through this campaign a long time ago and don't remember the details. But is Gem needed in this playthrough? The next mission will be with the Barbarians, and the one after that will be with the Fortress, and Gem will be there.

Well, it's clear that you can complete it with any hero, even Verdish. However, it's more interesting to play as our heroine, because that's how the game was designed.
Regardless, I'm disappointed with the situation, and I would appreciate some help.