Raven's Despair

I'm on my phone, so it's like this.
Thanks for the Walkthrough and feedback; it seems it turned out to be quite easy after all. I created this portal to somehow diversify the process when I realized where things were heading; I will strengthen these creatures that run out, as well as the final stage. By the way, could you send me the replays of the last battles in a private message? I'll watch them when I get home.
And, technically, this is my second experience in mapmaking; the first was the map "Counterattack," but it was entirely made by copy-pasting scripts from campaign maps.

Added 15 minutes later
Yes, and also - was the quest for reinforcements working properly? It was created to stop the creatures running out of the portal.