I didn't use any magic. The Dungeon is on grass. The arrangement is: 1 Troll, 7 Eyes, 1 Troll, 73 Trolls, 8 Harpies, Harpy, Harpy.
The losses were 2 Harpies and 3 Trolls.
If the hero had combat skills or a blessing, the maximum damage would have been even lower.
I think there shouldn't be any problems with Goblins on levels 10-15 either. :D