A long and complex scenario.

I don't know where to ask this, so I'll ask here. If necessary, you can delete or move it. First, if this hasn't been discussed before, which scenario in Heroes do you consider the most difficult? Why? I'll add my question right away. I'm looking for a scenario that takes a relatively long time to complete so that I can develop a Demon (or even another race, but I'm more interested in this one) using the "Call of Urgash" skill. All the scenarios I've played are completed too quickly. Multiplayer maps from the game are also welcome. If necessary, I play on Recruit difficulty; maybe I should just make it more difficult?