There is no problem if you want to pause for a quest and then come back.
If you are all ok, the quest starts... now.
Zargon is employing a new force! They meet in an abandoned mine deep in the mountains. I can't see inside, as some mighty earth magic is shielding my view. Go, investigate and see what is behind that shield. Every Hero will get 100 Crowns upon returning.

And I can imagine what the first command might be, so "open door" the answer is here:

That's a Beastman
















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