Demon invasion.

Here, on all the maps, there are mentors – in the first half of the first map, there aren't any, but the guards are tough. In the second map, the demon group has a terrible setup. :)

Having mentors on each map is good. I just don't understand (and it's not just you), how you count them – first/second. Are you counting missions or maps? For me, the first mission is bridges, and the second is snow, for example. The mentor on the second map is in the lower right corner, near the very first dwarven castle, behind the garrison. Dragons of Arkat guard him. Nearby, there's a library for them, guarded by regular dragons and dragons with Sandro's cloak. And not like Gerter wrote to me earlier, "in the middle of the map."
I have the cloak, and the mentor is mine. Finishing this map is just a matter of time now.