From the publisher's web site:
Alien horrors are terrible creatures from beyond space and time. Their bodies and minds conform to strange laws foreign to normal mortals. Possessing potent sanity-bending abilities and physical might, they are a threat not only to the stalwart adventurers who battle them, but to reality itself. This product includes tips on integrating alien horrors into your AGE campaigns, along with rules for three different breeds: the alien hybrid, the extra-celestial spawn, and the hunter horror. Also included are the alien horror template for customizing other creatures, a new focus (Eldritch Lore), and notes on using forbidden texts and playing an alien hybrid.