He waited a moment, allowing the first line to get through, before suddenly the flames seemed to... explode was the only way to describe what the wall did, suddenly going from nearly invisible and only a foot or two thick to nearly fifteen feet wide and high, and roaring like what hellfire itself would sound like, at least to him. Still a poor second to an actual bombing attack, but likely the most horrifying thing a troll could ever encounter. This wall grew lashing tendrils, that sought out the nearest trolls, and lashed them across the face and chest, something even the mindless undead would hesitate to walk into.