mrshch
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Just read it more slowly. It's hard to explain it any simpler.
Added 2 minutes later
Here's where it talks about the troglodyte in the Nagabanka.
"Thus, a two-unit stack may not attack in a situation similar to the "invisibility" bug of a stack behind a wall of fire: if the base hazards of the hexes are such that, in the best position to attack this enemy, the front hex of the stack will end up on a "hazardous" hex, and the rear hex on a non-hazardous hex, then this enemy may be ignored.
For example, you can add 100 djinn and 1 fairy to a hero's army; place a town (not a tower or a Stronghold, so that it doesn't have native terrain) with a fort and without a Stronghold, with 1 monster guarding it. Attack the town, position the fairy in the middle row, 2 hexes to the left of the gate (the farthest cell from the monster, so that it can reach the fairy), and have the djinn position itself. After this, the monster will not attack the fairy, but will only move so as not to be exposed to the djinn's attack. The reason is the same as with the wall of fire, only the role is played by the hazardous hexes within the djinn's range."
Added 2 minutes later
Here's where it talks about the troglodyte in the Nagabanka.
"Thus, a two-unit stack may not attack in a situation similar to the "invisibility" bug of a stack behind a wall of fire: if the base hazards of the hexes are such that, in the best position to attack this enemy, the front hex of the stack will end up on a "hazardous" hex, and the rear hex on a non-hazardous hex, then this enemy may be ignored.
For example, you can add 100 djinn and 1 fairy to a hero's army; place a town (not a tower or a Stronghold, so that it doesn't have native terrain) with a fort and without a Stronghold, with 1 monster guarding it. Attack the town, position the fairy in the middle row, 2 hexes to the left of the gate (the farthest cell from the monster, so that it can reach the fairy), and have the djinn position itself. After this, the monster will not attack the fairy, but will only move so as not to be exposed to the djinn's attack. The reason is the same as with the wall of fire, only the role is played by the hazardous hexes within the djinn's range."