How to get to demonis?

[player1]

Just try not to make mistake like me, when I run around hero who guards the entrance to Demonis to enter there prematurely (some death knight type hero).

Sure, I found some nice spells, increased leadership and got some experience while solving quests. All that without a single battle, since all stacks are way too hard. Luckily, it's easy to bypass armies on floating islands.

Unfortunately, whenever I tried to return to dwarven territory from Demonis it was game over for me. That hero I bypassed before would always attack me the moment I return from Demonis.

So... don't go into Demonis before dealing with that hero.