there seeing the wavering of the enemy by reason of the dread of the fall of gothmog the marshal of the hosts , the royal house laid on and the king came down in splendour among them and hewed with them , that they swept again much of the square , and of the balrogs slew even two score , which is a very great prowess indeed : but greater still did they do , for they hemmed in one of the fire-drakes for all his flaming , and forced him into the very waters of the fountain that he perished therein .