The griffin is immortal.

The second mission is a real nightmare, and not just because of its difficulty. I couldn't complete it with my main hero. I tried on Veteran difficulty. Vitia arrived on the 4th day both times, and, by the way, the fire warriors didn't reach level 5 either. But that's just the beginning. I can't seem to finish the mission. The problem is this: I couldn't build up the Angels for a long time because I didn't have enough time to gather troops to defend the mine; there were too few resources and money. Later, it wasn't critical to keep running back and forth to defend it (I should have been busy chasing down the demons), so I just gave up on it. When I built up some troops and managed to overcome the garrison, I defeated the blue hero. This probably backfired on me. While I skipped week after week while Markel gathered his strength, I went to take the gem mine, and here's a surprise – it suddenly turned out to be a quest-related mine, and a very strong one. This quest appears in the main storyline, but since it's already completed, it can't be closed. The situation is this: Markel defeats Aiden, it seems, but he can't get close to the garrison – the mission fails. Fiona can defeat the first Inferno castle, but the path to the second is not active. I even tried using a town portal to get to Markel and enter from there – the mission fails (when Fiona approaches the garrison, but otherwise they communicated and exchanged artifacts). I tried not touching the mine at all – the same dead end. Conclusion: the map is unfinished; it doesn't account for perfectly legitimate player actions that make it impossible to complete. People have already written about Durgal – he's useless (they could have kept him in prison and leveled him up, or given him a Tome of Darkness/Light, or at least a useful scroll), especially since he can only be freed in the late game. It would be good to display the tasks of the keymasters and the farmers in the tasks section – you don't always play continuously, and then it's hard to remember what they asked for. After the dialogue between Markel and Aiden, it would be good to show him (open him on the map) – they did meet, and also display Markel's decision in the tasks. It's bad to have Markel just sit and accumulate troops – otherwise, it's impossible to defeat Aiden (although I didn't have the patience to reach the number of creatures shown in the screenshots above). Unfortunately, my walkthrough ended here.

Added 22 minutes ago

I advise you to first make a quick save and outline Fiona's build, keep a notepad and write down the build; if you don't like it, restart until you have an optimal build...

And I would like more details from this point. Fiona starts the mission at level 1, with light, darkness, and a fallen knight.