Walkthroughs for custom maps.

since they can only move one tile due to the quicksand, the AI often decides not to move at all.
the AI seems to lose track of the target it can reach, so it goes into defense and stays in place.

That's great! Finally, I found the answer to a puzzle that had puzzled me once. I had a battle where, during the siege of the Citadel, the hydras remaining inside also didn't attack, even though until that day I was sure that the AI was programmed to always attack/move towards our troops. Similarly (if I'm not mistaken), the AI always casts at least something as long as it has mana.
Another useful observation: attacking with our clone against an enemy stack under Berserk does not remove the Berserk (just like a ranged attack), because Berserk only ends when the stack itself attacks the nearest unit, and if the enemy stack kills the clone by retaliating, there is no one left for it to attack (all our stacks must be out of reach at this point!). This is a good tactic for finishing off the last large monster stack in some situations (for example, protecting against blindness on the enemy hero), as it prevents the enemy from casting anything.