From the back cover:
Alien Enemies provides more than 40 alien villains and oddities for your Champions campaign. Discover the secrets of the Masq, a race of otherworldly shapechangers who walk among us. Wonder at the power of the Infinite Man, a being of limitless abilities who is making Earth his new home. Shudder at the horror of the Spores from Space-oozing, vine-covered zombies now stalking the shadows of our world. And tremble at the fury of the Tyrixx, insectoid invaders who have already laid waste to countless planets on their way here.