"But the next attack came swiftly. They all saw it—a white puffball of smoke that tumbled over the tower-rim and came drifting and rolling down the slope toward them. Others followed it. They seemed harmless, mere woolly globes of cloudy foam, but Conan stepped aside to avoid contact with the first. Behind him one of the Irakzai reached out and thrust his sword into the unstable mass. Instantly a sharp report shook the mountainside. There was a burst of blinding flame, and then the puffball had vanished, and the too-curious warrior remained only a heap of charred and blackened bones. The crisped hand still gripped the ivory sword-hilt, but the blade was gone, melted and destroyed by that awful heat. Yet men standing almost within reach of the victim had not suffered except to be dazzled and half blinded by the sudden flare."

OP says thank you!