No, it's just a building on the map that you can enter once a week. After visiting it at the beginning of the battle, a rain of fire falls on the enemy.

There is a building that provides a rain of fire, but in this case, my Ludmila and Moander were destroyed on the mission map, not in battle. Did you notice that during the demons' turn, a fireball falls on your friendly heroes who are within the influence zone of this city? I suspect that this is the action of a unique Inferno building, which destroyed my "roaches." I advise you to leave them at least a few weak units, a couple of skeletons in stacks of one.