Is this small passage worded and structured properly?

The Menzoberranzan force, known as the Army of the Black Spider, marched straight into the trap: the duergar were joined by Vhok’s legion and the House Agrach Dyrr soldiers, who turned on their brethren to inflict considerable damage to the drow army. The Menzoberranzan force was almost utterly destroyed in the battle, and would have been if not for the ferocity of the House Baenre troops. The remainder of the army retreated to Menzoberranzan to prepare for a siege while leaving a token force behind to slow the advance of the duergar and their allies.