looking through crystal balls , they saw a great variety of troops : men , both foot soldiers and cavalry ; obsidian monsters such as had appeared in kolistras neighborhood ; glass snakes of various sizes , that could become virtually invisible , by matching their transparency to that of air ; mechanical spiders of various sizes , the smallest barely visible , the largest eight feet tall ; great divisions of army ants , each ant being a finger long , with diamond mandibles and a poisonous sting ; clouds of wasps of comparable size ; amorphous creatures of stifling mist ; giant amoebas that could squeeze through the smallest cracks ; toxic mosquitoes ; fiery lions ; vipers of ice ; and many others .